Just an idea, but I would use a single high-torque servo, per wing, with a control "wire" that would span to the 1/3rd points of the flaperons... giving you dual-position control with only a single position force. You are familiar with the means most planes use to control the elevator?... a "wire", bent into the control surface on each end, with a "control horn loop" at the center. (or sightly offset to the side of the fuse.) This same type of design worked for me, using a single servo to move 30" flaperons. I can provide a detail illustration if requested.