I set a VGA adapter to run my IIsi Color Pivot in landscape mode at 16" resolution. Give that a try. IIRC BMOW worked out the signalling and we figured out a way to mount a ball switch adapter to a pivoting monitor . . .
After searching back through 24 of the 39 pages of Hacks:
Info you need starts about here:
With the ball switch (replaces what I'd assumed to be a mercury switch) trick you should be able to automagically start up in either mode? When the card detects the setting for either at startup it should work? Still fuzzy on that, but have doubts we'll get pivoting on the fly up and running. But SoftPivot(?) might find the way? Dunno, still asleep.
If you have, or anyone else has found related threads to add to my list, PLEASE do so.