Actually, strike what I said about the RA92 being the largest supported
disk.
Apparently SIMH supports an RAUSER disk that you can enable with:
SET RQ0 RAUSER=2500 ; RA82 with 2500 MB
or you can set block size
SET -L RQ0 RAUSER=5000 ; RA82 with 5000 LBNs.
So just set your RAUSER drives to the same # of blocks as your
MicroVAX 3100 drives, and I bet you can just make images of them and
they'll work.
-Seth