i am using the HX12K servos all around on my 50cc size wagstaff extra i converted to electric. I fly the snot out of it and they are working flawlessly. They work best on 6V, an require a large BEC (i am using a 8-Amp bec)http://www.hobbyking.com/hobbyking/stor ... dProduct=2
Also u probably already know this, but the rudder should use a pull-pull setup... with a regular linkage, when it pushes, the force if the pushrod combined with the drag of the rudder surface will want to tear it off (especially with a large counterbalanced rudder). My rudder is coming loose at the hinges, so i will invariably have to go with a pull-pull setup sooner than later.
Hope your project goes well!