[MPaulHolmes]

Sorry, I was away getting pinewood derby supplies for my 3 year old. "He's" going to enter the competition on Nov. 20th. hahaha.

I'm using 10 stth6002c diodes.

If you use a diode and resistor in series, the mosfet drain voltage will pulse MUCH higher than if you don't have a resistor in series with the diode, assuming paths are already at a minimum length. I also simulated that, but I haven't posted it. With a resistor it was 300v at the mosfet, and without the resistor it was about 140v at the mosfet.

I think your layout is the reason you are observing different results. I think you should have each diode/capacitor/mosfet loop as small as possible, because that loop has the fastest changing current on it. Everything else is a slop fest (meaning the other stuff can be relatively long).