RE: Hitec HS225 or HS85MG enough for Sundowner 50 ailerons?
225 is a decent servo for its size/weight/cost. The only issues I've seen/heard about the servo is a centering issue when using one servo to drive both ailerons (not normally seen under 130 mph), and issues when used in 3d planes with large amounts of surface deflection.
For what your using it for, they should work just fine. I 2nd the opinion on the 85's not sure they would hold up on ailerons, but I use them for throttle all the time.
I've used them on 5 cell packs without issue.