Well, finally I've got that fixed. I realized that there can be room for a full size pan if the front baffle is made thinner. So, with two layers of 3/8 inch ply I was able to make a new baffle, seen here with the original one:

Here it is with the grill cloth:

It mounts right in, with about a finger's width between the output transformer and the pan, and just enough room for the reverb cables. Interestingly, I initially installed the pan in the standard fashion with the input on the preamp side and the output on the poweramp side. This resulted in a huge level of noise which disappeared when I flipped the pan over with the input on the power side and the output on the preamp side. Go figure.
Anyway, now I've got the classic Twin Reverb drip back. For the speaker cabinet, I have a mid 60s Bandmaster bottom that was originally a two 12" cabinet. Fool that I am, I decided to shoehorn two 15"s in there. They fit with a bit of convincing as seen below. The sound is all that two 15s should be - lots of clean clear volume. The speakers are Weber neos.
