Dean, you don't need 4 servos. 3 is plenty, and you can even do it with two.

But first things first. Phread is correct, 1/3 of the aileron is plenty. You could even get by with a little less than 1/3 (Like about 8" on each side).

The PT-60 is designed to use torque rods in the center of the wing to control the ailerons. These will be used to control the flaps - One servo pushing a split pushrod.

For the ailerons, you can either use one servo in each wing, or one servo in the center of the wing pushing flexible pushrods out to the ailerons.