I didn't get in on the subject of whether these servos are suitable or not for this plane, because that wasn't the question, but since it has been raised, I'll give my $.02. I would not use the 425 on a 60 size that's going to be wrung out. For aerobatic flying, I would agree with Geistware, 605 on aileron and 425 on elevator. For 3D, I'd use the 605 on aileron and get one 545 for the elevators, or mount two 525 in the rear for elevators.
My reason initially to use the 605 for elevator was, that when you put a large arm on the elevator servo, to crank the elevators to +/- 45-70 degrees, which is my idea of 3D elevator set up, the servo is going to work hard to drive the elevators to these extremes, and the 425 would not like that at all.
I run 6V NickelMetal on all my planes/servos w/o regulator, and I don't get any jittering. I run it to Futaba, JR, Hitec and even Cirrus Coreless, all w/o problems.
I fly my S3G Extase with Cg 2"-2.5" behind recommended location, and I am still moving it back, (recommended is 5", I am at 7"-7.5" behind LE he he) but this is a long tail moment 3D plane, and probably much more forgiving than regular aerobats.
DKjens