Sorry for the huge delay, been very busy. Yesterday my Roland CM-300 arrived, which is technically a Sound Canvas 55 in a beige box. This means I can now record the music from games that were composed on the SC-55 (most of LucasArts's games for example).
Regarding SuperPlex, I can't see any support for the MT-32/LAPC-I on it (if there is I can't get it to even work).