retract servo suggestion needed
Well, the thing you need for a retract servo, is a lot of throw, and a lot of torque. By using a standard servo, you give up on both. If you swap out the standard servo, and go to a higher torque servo, you gain on the the torque only. The throw is still +/- 45 degrees or so. You do gain ATV adjustment capability, but the you lose on throw!
You could use 2 standard cheapo servos - each servo placed near the retract mechanism, to eliminate slop, and use a y-harness...
The right thing to do though, IMO, is to use the retract servo properly. I have a pattern plane that is probably 7 years old or so, and the Futaba S-136G (?) retract servo still works fine, for operaqting the mains, and the nose gear. The servo, along with the HiTec you spoke of, was designed for hi torque, capable of max throw per servo arm length (180 degrees - can't get any more than that...), and you even get a more realistic retract speed due to the gearing.
You could use air cylinders, but why make it more difficult if a single retract servo should work?
Good luck...