I just mount the horn so the holes for the clevis connection are direclty over the hinge line and on the movable surface so it's either in line with pushrod coming off the arm (aileron) or where no binding occurs (rudder, elevator) depending on the type of rods I'm using.

For trainers and other types with one piece elevators, it's works real nice tot have the pushrod come staright out the rear of the fuselage. Very clean and no hole in the rear side of the fuse for the elevator.