Cymbal choke MIDI

Hey,

I am somewhat new to Midi instruments in general.

I have an Alesis Nitro Kit with a chokeable cymbal that works fine when operated through the drum brain sound processor. When connected via MIDI to MainStage (or GarageBand), everything works except for the cymbal choke.

In MainStage I can see (and learned through grooming the internet) that choking produces a polyphonic aftertouch. I tried to map that aftertouch to the cymbal choke part of the drum kit, when now choking the cymbal, MainStage shows it detected the assignment, but it doesn't actually choke the cymbal.

Long story short: Anyone has had success using a chokable cymbal on an Alesis drum kit in Garageband and/or MainStage who could guide me through the steps needed to make this work?

Thanks,

Erebru