Yo @Oxbown !
revisiting this…
Should CC28 expect to be a 0-127 value or a delta?
hacking with @Gerald_Stevens today and we made a Mother compatible midi mode for the OMX-27. 
Wondering if there are other “Mother” patches that expect different things to emulate the encoder input. Gotta go poke around on the C&G forum and see…
EDIT:
Seems like the Expression and Foot switch CCs are somewhat out of sync with what the organelle does… and that overlaps on CC26
FWIW - here’s the Organelle MIDI info. The C&G Desktop Mother patch does the same
The Pedal Port
A pedal connected to the Organelle’s Pedal port transmits two sets of “control change” messages.
Controller number 64 transmits a controller value of 0 (zero) for any received signal below 64, and a controller value of 127 is sent for any received signal of 64 or above. This discrete, threshold behavior is particularly good for sustain-/damper-style pedals.
Controller number 26 transmits continuous values. While the general range would be from 0 (zero) to 127, the exact range of values may vary based on the pedal connected. This continuous behavior is ideal for an expression-type pedal.
Is anyone out there using the footswitch or expression CC inputs?