Well, you would not want to put your throttle on a switch of any kind. You could put the prop servo on the flaps channel or a retract channel. better to put the prop servo on the 3-position switch if that is your last channel. Forward neutral and reverse is better than zero, midrange and full open, IMHO.

Good luck. I am not qualified to fly 3-D yet, but I fly every day so, maybe someday.

Oh..... and I will sell you a 'flux capacitor' cheap.