Here's what I've got so far. I'm just playing around with this and haven't decided if I'm going ahead with it or not.

The two blocks are identical. They capture the music wire and will bolt to the top and bottom of the former behind the wing. The lower block will be glued in place permanently. The bolts are just to help clamp it while the glue dries and some added security.

The top block will remove so I can pull the assembly if needed. I plan to use 1/16" music wire with Z-bend at each end to hook up the bellcrank to the servo. All that seems to be fine. I'm just concerned about the fiberglass board cutting through the wire.