Re: Servo motor speed control--Wizcrafts was on the right track; DDahl solved the problem in a very simple manner in another thread here on Leatherworker a few months back, but amazingly, the solution was generally ignored.
Fortunately, Larry from Southwest Florida Holsters didn't ignore the solution and posted a 'how-to' on his website and also spread the word to a few other forums, including this thread on hotrodders.com, where I came across it. I modified the solution a bit (detailed at the end of the hotrodders thread), but the principle is the same.
My motor now goes from a speed of "1" up to "15", the max I have set, EVENLY OVER THE ENTIRE RANGE OF TRAVEL of the speed control arm, not just in the first 1/4 inch like it used to!
All the links above contain the answer to your optical speed controller sensitivity problems on the various servo motors.
--Mark