I am a bit lost too, that is why I asked
Not finnished with my book yet but I will try to explain why we "modern" people fail to find the connection.
Humas are notoriously lazy and happy for a long time once they created something great.
Take the car....
We observed nature and the universe for our first big inventions like the wheel.
Later we found more and more things in nature that are important but wee needed a way to express, understand and to put into into a language.
Math was "discovered" - it tanslates what can see, feel and hear in nature into something we can handle.
One and one makes two...
two times two equals four...
Add decimal parity and most basic math already forks fine.
Later we needed stuff like volumes, areas, angles to "invent" more complext structures and technology.
As a result all we know from nature was put into relating formulas, sequences, "fixed" numbers.
The laws of physics, the golden ratio, binary systems and parity, Fibonacci sequence, sine waves!
But the lazy human stopped evolving math the same way he discovered the connections in nature through observation.
The "simple" math was just expanded by more and more complex formulas.
We tried and still try to understand the energy triangle in nature but at least Einsten found the formula E=MC² to put it into a mathematically useful form.
No matter what, math will always be our translator for nature.
So a lot of possible pathways that nature provides us allow us to theorise about how things should be and develop technology to make it real.
Or to fail and find out where our math was wrong.
Technology however is based on the same flawed math that we simplyfied and now no longer care about but we invented calculators and computers to do it for us.
We used to visualise math back in the days...
Ruler like calculators to use sliders to show the relations in trigonometry.
tables to show us relations between certain sequences and fixed numbers like Pi and other "constants".
We ignore nature and also lost the visual aids that previously helped because using modern technolgy is faster.
We learn more and more to unlearn math by making it easier to use it.
And our modern understanding of technology does the same to us.
We copied the binary system from nature to create calculators but we ignored to add harmony and resonance to it
And because we are lazy we also reduced the basic function to ZERO and ONE instead of including our well know laws of physics, seqeunces and harmonic spirals.
It works, so why bother, we just write enough code to compensate and again base it on the already lazy and flawed math that has lost harmony and resonance.

If Einstein and Tesla worked together as close as history make us think then they obviously exchanged ideas and theories.
If you put our understand of the most basic math into a circle then we end up with the energy triangle 369, the parity numbers 1, 2, 4, 8, 7, 5 and two circles that also form a perfect sine wave.
Both genius minds had the same common language: math.
One was driven to explain energy, the other tried to understand harmony and resonance and invented electricity to prove his version.
If math is the common language (like we learned a second language like french in school) than the the other tow, energy and harmony/resonance can be translated.
Of course there will always things that get a bit out of context or just won't ranslate properly.
We know that when we try use online service to translate lets say a chinese website...
So it is no wonder they both came to their big breakthroughs around the same time...
And is we look really close....
E=MC² ,C is the speed of light, a "fixed" number.
It is also a frequency, a wavelenght, energy...
It is harmonic and resonant.
Einstein might have failed to explain why C² is the same as mass, but 369 shows mass is nothing but a form of energy.
He explained the triangle without putting E M and C onto the corresponding 3, 6 and 9.
He was happy to have solved it, we just needed to figure it out too
But if C and M are both the same, the opposite and their sum then harmony and resonance can replace both for the use in math.
And for electricity in harmony and resonance it means there is no loss, there is no chaos.
And in a resonant system all energies would amplify.
Since at this stage it would still lack the parity harmony and resonace translate the missing link.
This explains why Tesla was also obsessed with the ratios 1/4 and 3/4 - which becomes obvious once you bring the sine wave, or Yin and Yang in relation to 369.

And for those simple above reasons I came to the conclusion that a transformer as in Tesla's late patent is only half of the patent.
It can only work with a tuned Tesla transformer as the power source.
And it has to be in a 1/4 3/4 ratio to work as described in the patent.
There is no way around it with math and E=MC².
Both system must share two links.
The topload of the power source and the individual RF fields from both individual transformer.
Otherwise 369 would not be complete as in E=MC².
And Yin and Yang or our sine wave just proves it
Or why else would Tesla have made the step from mechanical resonance (mass) to electrical?
Mass is energy, so invent AC electricity as a form of energy to replace it.
Quite obvious if you thing about it the way nature shows us, instead of using a flawed math system to understand it

18 pages, font size 12, 39 chapters so far...
I have the right numbers, I have relations, I have conclusions, I have "proof".
3.3.3.
I need the 6 as more than a result of mathematical relations from what I have so far.
330 chapters more to reach the 9.
The remaining chapters must be equal in numbers but also add up or relate to 6 and 9 to come to the right conclusion and understand math as a language.
The relations to next sets of chapters and pages should result in harmony and proper realtions.
Maybe 1/4 and 3/4 ?
Or with a pattern like the Fibonacci sequence?
Maybe a combination with PI, but then it would be too cryptic, if you know what I mean
Maybe I realise my patters for the first 39 chapters was flawed once I can make more connections and relations to form a more complete picture?
Einstein was right, it all is RELATIVE....

I would try using a lossy ferrite bead for the gate resistor or in addition to a small gate resistance. 

That is actually a really great idea!

The -12V from an ATX is not just weak but also not really suited to join the +12V rail.
The first if for data purposes, the second for high power use.
I would not be surprised to see the voltage break in quite a bit.
No matter the supply I always found it beneficial to have a beefy electrolytic cap close to where the gate drive draws the most power.
And some switch mode power supplies really hate going from idle to full load.

But I agree, some schematics could help to figure out where the culprit is in this nice design....

When I started with Tesla coils ages ago I only used spark gaps and neon transformers.
Now I try to step up to SSTC's and later on want to go DRSSTC.
But one thing still stumbles me when it comes to the phenomenon of resonance :

I might be wrong with how I understand it, which could be part of my problem LOL
Back in the day I learned from a few old blokes how to build Tesla coils.
And they explained the stuff like this.
When the spark fires and closes the circuit the stored energy from the tank cap will cause the coil and cap to swing at their resonant frequency.
The amplitude starts strong and then fades down until the spark extinguishes.
The secondary is forced to act on the magentic field changes and starts to swing as well until the voltage built up is high enough to cause a break out.
So far that was always easy to understand.
But then I was told that while both coils are swinging the secondary also transfers energy back to the primary, which in return causes a longer swing time.
Would mean not just a single lightning strike but a succession of multiple strikes until the energy levels are too low.

All this happens with nice a nice sinus curve.
But when we go digital we often use measures to prevent boltage from flowing back into the "switch" with diodes and other filter measures.
With a SSTC we force the primary to swing at the resonant frequency of the secondary.
A DRSSTC has both sides in resonance.
But what happens to the additional energy transfer between the coils when the secondary would transfer some back to the primary?
I mean with a forced and constant signal this additional energy should cause the voltage in the primary to go even higher than with a spark gap.

What started as a simple and fun project starts to turn into a mental nightmare for an old man LOL
First I thought I only need to know how my mains voltage creates nice arcs from my secondary.
For that I need to understand resonance.
We deal resonance both for the magnetic and electrostatic field as well as for the radio waves.
Ok, slightly more than planned but managable...
Then came magnetic coupling.
With that coil and field properties.
Also standing waves, self- and layer capacitance and grounding of RF power...
It is soooo much easier doing it just for fun instead of trying to fully understand what happens and why it happens

By the way: Is there any easy way to simulate the magnetic field of a coil or two coils like in a Tesla coil?
What I found so far is far too complex for the old man behind the keyboard.
Was hoping for something that allows to create a coil or to import a 3D model of it, add some parameters and see the magnetic field on my screen.
So without endless calculations and the use of multiple programs to create a video from still images or screenshots.
I guess my chances are slim to none?

Ahhh, I feel your pain.
Had to go to a dedicated plumbing store for mine.
But if you have some left overs, an oven and something to cut PVC with...
Cut pieces of your pipe off that are longer than the diameter.
Cut these pieces with a hacksaw lenghtwise.
With a flat sheet or tray in the oven and preferably a sheet of non stick baking paper you can now heat the cut pipe sections.
A temp of 180 - 200°C should suffice to get the PVC soft enough.
First try to make them unroll.
Then move and turn them until the pipe looks like a flat sheet, more or less at least.
Take them out while still soft and use a dough roller, bottle or similar to really flatten them on a wooden board.
Once cooled and hard cut a disk out to fit tightly into your pipe.
(does not need to be perfect)
Use standard PVC glue and primer as directed on the packs to glue the disks into place.
First one is the hardest, so here is how to cheat:
As you should have a rig for the winding, use it
Place the first dis inside and align it so if you spin the pipe it won't wobble.
Using a brush apply some primer along the joint area, don't soak it though.
Add a bit of glue in tree or four points, only a little bit!
While slowly spinning spread the glue to a really thin layer - it will dry quick...
Make sure the disk won't wobble and let this first bit of glue set.
The second disk will be inserted dry after applying a thicker coat of glue to the disk inside, cover the entire surface as thin as possible but thick enough to fill imperfections.
Push the second disk in and use a rounded pin or similar to push it against the first disk while all is spinning slowly.
You should see a small amount of glue coming out the joint area, wipe it off or spread it out.
Once all is set you can fill the remaining gap with resin for added stability.

A quicker way to cheat is to use a wooden disk.
Cut and sand it for a an easy fit, so leave a gap big enough so you could wrap a single layer of paper around the disk.
Use Chloroprene cement, also named shoe glue, neoprene glue, to make the connection.
Brush the joint area on the wood with some acetone, you want a slight wet look without soaking the wood.
Before it dries apply a coat of the glue and spread it evenly to get full coverage of the wooden joint area.
Prepare the PVC by wiping PVC primer over the joint area.
Before either fully dries press the disk into your pipe.
You only have limited time for adjustments and I find it beneficial to just place the disk on a non stick surface and then to slide the pipe over.
For bigger ones secure the disk with a screw for added stability but please through whatever it rests on into the bottom and not from the top as you need a bloody long screwdriver to get it out

So you are saying that apart from looks there is no realy benefit?
Id a pipe cage performs as good as a real toroid then I might have to reconsider my approach and go for simple instead.

Nice designs and sparks indeed!
I see you are going in similar directions with your thoughts.
There must be a better way somewhere..... LOL
You already noticed that simply adding some caps or splitting coils not always results in all the desired effects.
Maybe something from my army times give you and idea where I am going here:
For our radio equippment we often used quite powerful transmitters.
And literally everything that was RF HOT was smooth and rounded with no sharp edges anywhere.
After a quick and dirty field repair the inside of our transmitter was glowing everyhwere.
Range was very limited, static in every transmission.
Only because we had to get some covers off and nothing to create smoth seals that are fully conductive when done.

Every straight piece of wire running at the resonant frequency will act as both antenna and receiver.
Means all connection should be rounded with no sharp bends or pointy bits anywhere.
Makes it hard to implement capacitors into the coil unless the coil itself is designed to have enough self capacitance to do without any additional caps in the resonant circuit.

A long time ago I experimented with magnet coils to see how different designs affect the magnetic field strenght.
Most of it was of course multilyered coils and quite often only for DC use.
And to judge anything I only had a compass or two and some fine iron dust in a clear plastic container.
The one thing I remember most is a coil from an old analog TV.
For some reason this old BW model had coils around the tube in seperate packs.
Without the curvature see them like a trapez in shape once flattened.
Like with conical primaries on a tesla coil the megnetic field could be elevated from the center of the coil by using different angles.
But if I used two of these coils with one fully vertical and the other angled, the megnetic field would be more like a funnel.
Bottom part basically like a tube and then expanding outwards on the top.
I think a similar effect coul be greated by using a seperated bifilar coil.
One winding cylindrical, the other half of the bifilar conical, so no flat coil anywhere this time folks....
I admit that I have no clue if the inductivites for both halfs should be matched.
Same for wire having the same wire lengths by the way.
But I do know that in general and with no regard of RF or coupling effects to each other that:
(only from my eperiements in the DC field!)
1. The magnetic field is very strong and powerful in the region from top to bottom of the vertical coil.
2. The field is quite uniform in strenght in this region too and in a circular configuration should be tunnel like.
3. Above the two coils the tunnel expands like a funnel, the angle of the conical coil affects the angle of that funnel.

If my thoughts are correct than, at least for a stumpy, it should be possible to have the magnetic field of the primary circuit overlap the electrostatic field of the topload.
It would be beneficial if the secondary is designed in length to match the wavelenght (at least IMHO).
We would have a magnetic field that full encloses the secondary before spreading out too much.
We would also have an electrostatic field, which I see as beneficial here, that overlaps with the magnetic field tight where coil and topload meet.
As everything in in resonance I assume the overlapping fields will extend acrs away from the topload.
So instead of allowing to go straight down with a risk of hitting the secondary or primary the arcs should act more like water coming out of a horizontal hose opening.
The more power the further they are driven out before going down to ground.
Well, at least in my theory of overlapping fields and harmonic relations

Before I try complex configurations I really want to compare some basic design first.
For me it was always easier to understand these things by actually doing them.
You know, start with a square, round up some edges, make a hole in the center, round and smooth the outside a bit more and in the end I call it a wheel

I like the idea of your mods, never thought of going this route.
At least not with additional coils in the primary circuit.

I have to assume that you used secondaries with a much smaller diameter before.
With your nice stumpy design, how much of a difference do you think makes the bigger diameter compared to a longer and thinner secondary?
Asking as I am still playing with the idea of making a much shorter secondary than yours but struggle to make or obtain a suitable toroid.
Might have to make a pipe ring cage if all goes down south LOL