This is my second SSTC. It uses a similar circuit as the first (in that there is an antenna for feedback), but with some very good changes. So far, the coil was able to produce 21" sparks at about 1600w input power. I am driving the IRFP260s (200V) right on the edge at 120VAC (170VDC!). So any voltage spikes must end up heating the MOSFET device itself. So far, it has proven completely reliable.  I am sure that having a driver that is always in tune helps a great amount! The power from this setup is just amazing. You will find that a different gate driver scheme was employed.  This gate driver, while being more robust, does suffer from a shoot-through condition and does waste power, but it does work will despite this drawback.  I also used a TL494 thinking that I may want to run the coil "open loop" with a simple VCO controlling the operating frequency.  I in fact never did try this.

The specs for the actual tesla resonator are as follows:

Secondary: 4.5"x18" winding of 30awg magnet wire.

Primary: 6 turns of 12awg on a 6.3"dia x 6" tall form.

Toroid: 8"x1.5".