Brian,
First off, what are you wanting to do with this aircraft? 3D? Imac? or just putt around?

If your going 3D you'll need good power:

For rudder you can use ONE!! Hitec 5745, 250oz at 6v, yes 6 volts, don't use 4.8 for digital servos.

use Hitec 5945's for your ele, One per

now for the ail... If you build up the wings you may need two per wing, (Hitec 5645, or 5625) because of flex, but if your using foam core wings you can use one Hitec 5955 per wing. Center it on your aileron.

Now most of the problems asso, with digital servos, is a lack of power and the ability of the batteries to keep up. So use a good Battery system like Formeco.

http://www.fromeco.org/

The settup I just described I have used on all my 33% & 35% 3D aircraft.

Scott