Elevator trim tab
I attached the hinge to the trim tab, using 0.016 shims for spacing to keep the hinge barrel from rubbing against the trim tab. When attaching the assembly to the elevator, the shims kept falling out so I taped a bunch to the trim tab channel so it could be positioned more easily. Then I drilled and attached the hinge to the elevator.
I then positioned the servo on the underside of the top of the elevator skin and drilled it into place. Unfortunately I initially put it in too far back, and now have 2 stray holes. These will have to be filled with rivets.
I shortened the threaded rod to a length that will allow it to attach to the trim tab, and positioned and attached the trim tab horn.