You might also consider the 3152. Looks similar to the 3050, but has nylon gears, slightly less torque spec.- 87oz, and less $. I have run these on a smaller plane on 6v for ailerons, elevator. If weight is not a concern, the 3151 or 3152 can make a good throttle servo as well. You may want a bit more torque on the rudder though, depending on your flying (F pattern?).

My opinion of the most critical surface would be the elevator....for obvious reasons...but also because servo centering and holding at center is key to smooth exits from end box manuevers.


good luck,
mark