Get some DuBro no 618 4-40 Rigging Couplers. They are 4-40 threaded pieces with a hole drilled thru the end. Then you can hook a 4-40 ball link to one end, and a 4-40 clevis to the other, with some SpiderWire in between. On something as small as a Fun-Fly, you could run the servo without a bellcrank..