Can they both be routed to the SAME DSP, or is it hardwired to be one per part?

If the former, surely when you change the speed, it should affect BOTH sets of drawbars.

Mind you, the old two Leslie (one for upper manual, one for lower) trick made for some great sounding organ tones! Nothing in this world beats sitting at a B3 in the middle of a pair if 147's!