gtbcpa

I have a couple of EDF 3 channel jets that I want to use a gyro with on a 4-channel receiver. Since the jets have no rudder my thought was to use that unused channel to operate the gyro with one of the radio's 3-way switches (gear or aux). Is it possible to reassign the gear or aux switch to operate from the rudder channel on the receiver? In reading the manual and going through the "Device Select" screens I can't figure it out. It looks to me like you may not be able to mess with the four basic functions (thro, elev, ail, rudd). Thanks.