Use the ball link on the servo... and have the pushrod connect to the control horn with a Z bend. Have the main rod on the inboard side of the control horn. (reduces the angle a little)

The horn not being directly above the hinge line wil just give a "differential" throw. With the horn behind the hinge it will pull more effectively than it will push. The big problem comes if the horn is so far back that the pushrod binds when it hits the hinge before you are at full push deflection. When the rod hits... thats as far as the surface is going to deflect.

You can correct for the differential at the servo, by having the arm offset the oppsing direction, the same angle. (this would aggrivate the binding problem above...)