RE: Is your WH Edge "snap-prone" ??
Shogun,
I've set up both an Edge and an Extra so far. Both with excellent results. As far as servo arms are concerned, I am using 1-1/2' aluminum arms from SWB. The ball link to center of output shaft distance is 1-1/4". That's on all of my flight surfaces. My rudder servo is mounted in the tail for a direct hook up. For the pull/pull arrangement, you will need a 1-1/2" "double" arm.
The distance betwen the servo output shaft and the ball link or clevis on the servo arm. should be equal to, or less than, the distance from the control surface hinge line and the linkage mounting point on the flight surface. This maintains a 'mechanical advantage" to the servo. Note that the measurement is fron the center of the flight surface hinge line. Not from the surface of the aileron, rudder, or elevator.
For general all around sport flying and mild 3D, there is no need for the longer servo arms. Both planes are excellent flyers at low to medium rate settings if that's what you desire. As a matter of fact, hovering only requires low rates anyway.
Enjoy the plane. I know I am!