I've just tried this on my 18MZ WC and it all works fine.
Select New Model
Select Wing Type 2 Ail & Norm Rudder
Select MULTI for System Type
In the FUNC menu move Ail 2 to channel 2 - so channels are ch 1 - Aileron, ch 2 - Aileron 2, ch 3 - Throttle

Then check in the Servo Monitor and all works as it should.

modtron
Oxford UK