What about the Q630/LC580? It has 4MB soldered on too, and is frankly a more full-featured platform (IDE, CommSlot, Video in/out) than the 605 or 575 boards. Has anybody tried a 128MB SIMM in there? Any reason to believe it would work any differently?

I'll have to snag my dad's 63x from his office at work and get it to Uni for recapping/experimenting.