I would think that the interplane struts (if the dimension is equal on both sides, and you allowed them to maintain the same positive stagger) (relationship of top to bottom wing) should not affect the aileron. It sounds as if you are forcing the wings to pull, distorting the wing and inducing a warp of some type. Try measuring from the top of the lower wing saddle (fuselage) to the top of the cabane saddle, and see how close this measurment is to the length of your interplane struts that you made. From the picture that you posted it appears that the top wing is flat, and the bottom wing has a slight dihedral, so the above statement may not be true.

Are the measurments the same for both sides? It may be due to the perspective of the photo, but I wonder... Check the dimensions for both sides. They should be equal, and the struts are to maintain dimension, not alter the dimension and cause the wing panel to move. Hope this helps.