I looked into the specs - it's similar to 3E in that it maps ROM or RAM by writes to zero page addresses, and also similar to E0 in that it uses 1k blocks but there is no fixed bank except on boot. You can switch any bank into any block. Still, 4A50 is far superior and requires about the same amount of hardware to achieve.
Assuming the problem is not on my end (I will look at my code again), is there any chance MC support can be fixed? It looks really promising with it's 128K ROM and 32K RAM.
The problem with these RAM schemes is that the creators aren't willing to produce hardware until a game exists, and programmers aren't willing to write a game for hardware that doesn't exist in large enough quantities and for a reasonable price. Hopefully, the Harmony/Melody will break through this barrier.