Eric,
You can only assign CC94 Send which is the DSP1 Type(s) assigned to the style that you will be using the Multi pad with. We cannot assign (any) other DSP processors to Multi Pads... unfortunately. Even inserting the controller CC94 is an undocumented feature of Multi Pads. We can also insert other controller messages for Expression, Attack, Release, Filter Cut-off and Resonance, etc to create other effects and to modulate or modify the MPs.
Another undocumented feature is to insert a second Voice message to alternate between 2 Voices in a single Multi Pad. You can do this type of programming using MixMaster or in StyleMagic's Piano Roll. Just change the file extension from .pad to .mid (or just add .mid to the file name) in order to load the file into StyleMagic, then change the extension back to .pad when you are done.
Joe H