Walt,
This may or may not apply but would be of general interest.
Because I have 10 keyboards here in my recording studio, I have a lot of expression pedals too.
I bought the new PSR9000 keyboard but did not buy any pedals. I was able to use some pedal switches that had the correct NO or NC, I forget which, with no problem. However I had a problem using foreign Expression pedals. I tried Korg, Technics, and others and I could only get what I though was a unacceptable volume. Yamah replied to me but offered no help. I finally got off the dime and bought the Yamaha pedal and wow, twice as much volume.
Apparantly different pots in the pedal. Live and Learn
Bebop