We'd suggest that you use a condition where the retracts are disable except when you're in takeoff and landing mode. The condition would turn on when the stick is lowered below a certain point. In all other conditions, you set the retract channel's AFR to a flat, horizontal line in all other conditions. That line will be offset to the retracted point. You must be sure to set the retract AFR to "SINGLE" in all conditions.

We'd debate the wisdom of this feature because the gear will go up and down as you apply or reduce throttle on a bad approach or when you go around. It's better to just have a condition where the gear is always down when the switches are in a particular position. Any setup can be defeated with a small misstep...you could have a switch mis-set, and be running the engine on the ground. Operate the throttle and the gear goes up. Better to just have the gear on its regular switch and make sure you have it properly-positioned before you turn on. We like the idea that all switches go forward...away from you...when the model is on the ground. That makes it very easy to insure the proper configuration of the model. Then, you don't touch any switch while on the ground.