ORIGINAL: pimmnz
Might be easier if you just forget the surface the stick operates, but lets call it 'direction' and 'speed' and 'height'. That way whatever surface controls the direction of the thing gets hooked to the stick that operates that channel, 'Speed' is then hooked into whatever stick controls the elevator, and if you are using an engine, then 'height' just gets plugged into whatever stick operates the throttle or speed control.
So, if my plane is flying straight and level at half throttle and Ipush the "height" stick forward is it going to climb? The answer is maybe a small amount, but it's largely dependent on the type of plane, wing airfoil, etc. The most noticable change is that it's going to go faster. Similarly, if Imove the "speed" stick, the most noticable change will not be speed, it will be altitude.