When you add more than 512K in the trapdoor you need to add an additional line or two from the card to Gary or the 68000, because there aren't enough address lines. Does your card have this? I had a "Baseborad" with 4MB in the trapdoor and ran into compatibility problems with certain software. I then went back to the 512k and a Supra expansion on the side bus, worked muck better. I think the internal expansions are kind of "Hackish" :-).
