AKNick with your 2" servo arms on the wing, and the servo arm centered, the control rod is not 90 degrees to the hinge line. Is this how you set it up? I know you mentioned something about 'equal distance'. Still learning here.
Well you have four goals.
1: full deflection flaps
2: 3D rates
3: the ailerons and the flaps moving at the same rate of travel.
4: geometry for the best torque.
You achieve 1-4 by using 1.75” servo arm on the flaps and ailerons.
If you use 1.5” you loose torque, flap deflection, geometry. If you use 1.5 on the ail and 1.75 on the flaps you loose symmetry as one will always be traveling at a different rate as the other which is not ideal for full span ailerons.
So adjust your end points so they are equal deflection. The use a curve to match and mix throughout the travel if necessary. Adjust your rates as necessary from there.
Also the control horn is so far away from the servo bay making this happen... poor design really.
Does that make more sense?