Hmm...  If anyone ever comes across a PMAGB-B that supports the VR299
scan rates (or VR290, for that matter), or has one spare, I'd like to
buy one.

Can any of the PMAG-A, PMAG-C and PMAG-D/E be tweaked similarly?

(Monitors are large and heavy and don't stack nearly as conveniently
as CPu boxes, and the one I have is a 1024x876 that works with all of
3100s, CFB, Vaxstation 2000 (and 3100?) video, and IIRC, can probably
be retuned into running with the 1024x768 video from the Maxine
baseboard video. At least, I've gone the other way with old hp300 monitors).