ORIGINAL: tschuy

If it were me in this situation I'd do one of two things. First move the linkage are closer to the senter of the servo. Doing this will require more movement of the servo to open and close the flaps. But it would have more mechanical advantage (less torque needed from the servo to move the surface) but would require more servo arm movement to achieve the same flap open distance. Option two would be to switch to digital servo's which tend to have more torque but also can be very pricey... the only other option is as stated by Sessholvlaru. But I would work for a secondary linkage advantage in the the same bay as the flap servo.