I just got back a new board with more memory. I swapped it out in the plexiglass and turned it on. We have a Sharp 800x600 SVGA display. The display was set for 640x480.
I changed the entries in the reg and hwt files. I rebooted. I get an upside down display.
Hmmmm...I can confirm that JP2 and JP3 were NOT shunted on my new board. However, my old board had a shunt on JP3.
A quick pull and push and, presto, I don't need a mirror to read my display. Good thing, too --- Driving that mouse upside down was starting to make me crazy.