Paul, there are several manufacturers of servo arms that are wheels instead of a conventional arm. I've used them and really love them. I believe that the ones that I used in the past is put out be Hanger 9. The cable is looped around the far side of the control surface and is fastened in the center of the circumference of the wheel away from the control surface. I really liked them. The ones that I used were Aluminum. I don't think that there was much, if any, weight difference between them and standard plastic arms, though it may be more important to you on a 25-size