Thanks for your comments, Al.
Yes, it was silly of me to put bleeder R's across those caps.
Many year ago I touched a non bled 16mf at 400 v and that has influenced me ever since
My ground plane is 2 earth rods driven into the ground just outside the window 8 ft apart.
The run to these is near straight (no nasty inductive sharp bends!)
Regarding layout.
There are many great layouts to be seen on the net of course, but
look at this one built by a very experienced Czech coiler.
It's a full bridge running up to 1,400 watts and works OK.
Quite a birds nest of long thinnish wiring to his 4 IGBT's, spaced apart in each corner.
None of my inter mosfet wiring is longer than 2 inches. as you can see.
(The long leads in my pics are, of course, the 12v supplies for the 2 cooling fans. )
Regarding driving the mosfets. I'm using a dual mosfet driver, UCC27425, driving via the GDT.
The GDT is only 2 inches from the mosfets so leads are, again, short.
BTW, my driver board is shielded from the sec coil.
I did blow a mosfet but that was due to an incorrect connection.
There is a fault on the driving board as no signal comes thro' to the GDT from feedback.
I have just finished making another board for the second SSTC and this is working OK.
So will do a swop for the dud one, then the sparks may fly.