Someone on the KRNet made a suggestion for a trim tab servo. They thought that a motor out of a remote mirror on a car, would work. Well, I don't know if they ever tried it, but I did.
This system works very well on the ground, and now, I can tell you that it works very well in the air. So far, 10 hours, I have not noticed any issues associated with the use of this motor for this purpose. The total cost was under $10.
Summary Description
Basically, all the stuff from the bell crank on the tab, to the screw drive, are model airplane parts and can be found at the hobby store. The really hard part is the threaded rod end that replaces the screw drive from the mirror motor. It was quite convenient that the threads on these are the same. you have to drill a hole in the end of the threaded rod end and solder in a 4-40 threaded rod, that then screws into the drive shaft that goes through a sheathing like a soda straw. I think that sheathing is something else that came from the hobby store.
Click on any pic for a full view in this window.