i vaguely remember there was some key combo to force u1mb to reload partition table, you might try that in scenario where ide emulation is enabled but you still don't see the partitions
the bigger problem is that i just realized that doing shift-s does not set up any other emulation (like atr), i should change it to behave like "space with ide enabled"
just out of curiosity, does mounting atr, launching s2sdx3.car (to enable ide emulation), forcing u1mb to refresh partition table and then running sdx from u1mb menu (with autoenable disabled so avgcart ignores all those reset keypresses) get you there?