Picture from work in progress (if there ever was anything else). I can now start the Super-Carbon without using the Variac.
Initially, the PSU SicFets blew up during startup when doing a full power on, very similar to what SimmConn reported here:
Presumably my SicFets ventured outside their SoA during startup. I'm not using the Cree C2Ms here (though it's a similar spec'd SicFet) and I have the current sources set for 25mA which might be pushing things a bit, so this particular problem may very well be unique to my build.
However, since this forum has a lot of clever participants , the solution was at hand in the same thread. As per @Kerry's advice, I wired in the depletion mode MosFet current limiter directly after the pre-reg caps instead of having it after the post-reg caps. Also, I added a Vds clamping Zener as per @simmconn's mod.
Not skilled enough to tell which mod did the trick or if both are necessary (and one can of course never exclude the possibility that it now works for some other reason that I have no idea about), but anyway it now starts up without anything blowing up and I can move on to the "oh, I'm supposed to listen to it?" bit. Special thanks to Kerry and SimmConn (in addition to Kevin designing these things in the first place); I would not have figured this out without you!
Apologies to all UK members; haven't gotten around to finding a new picture host yet.