OH YEAH I forgot to write this down in the docs but before any of you try to make a backup copy of the 1750 (or restore it), disable RAMDOS first so that STASH, FETCH and SWAP are sure to work. Don't just do a "SYS 65418"; you have to disable WsDos as well. The "KILL" command does this correctly, and of course there is always the power switch.
It was actually just luck that it CAN support expanded systems. You see, when the reset button is pressed, the low-byte of the jump address contained in 1FFF8/9 is still in the accumulator at the time the jump to FF7FA occurs. That would be $FA. This winds up being stored to $FF00, and just happens to always jump into bank 3 because the two uppermost bits are set (you can check the reference guide to confirm this). Since any read or write to bank 3 is mirrored into bank 1 on an unexpanded system, the CPU always lands in the right bank- no matter which memory architecture is in place.