Picture a box, you want to grab one side in the middle pulling it back and when releasing and arrow hit the other side, obviously your not doing that, but that's the goal.
The movement of the rest is one way of getting that center shot. If you feel your abilities are good then step back tuning will tel you if your rest is in the right place (as long as there are not other things).
Stand about 10yrds. away from the target and shoot one known good arrow at the target. Take a level and put a piece of tape on the target plumb over that hit. Step back to 20 yrds. and shoot again at the same spot you AIMED at before, it should hit the tape maybe lower but the on the plumb line. If it doesn't don't worry. Step back to 25 and do the same as before. Continue stepping back as far as you like. Raise your aim on the spot if your dropping out of the target, but plumb with the aiming spot.
Something will start to be evident. If your hitting the other edge of that imaginary box your rest is in the right place horizontally, if it trails of to one side or the other the rest needs moved in the opposite direction. You may think moving the rest in the oppisite direction aa no brainer, but when you get the rest right and go to set the sight if you do the same you'll be wrong, Setting the sight requires chasing the hit not moving the opposite direction.
Move the rest to get the arrow impacting the plumb line from any distance. Your rest is now set to the setup you currently have horizontally. You still haven't determined if your pulling in the center of that imaginary side. If your not the arrow will not g through the air the a female Chinese diver entering the water without a sound or splash, not to mention your wasting energy and the that means speed and noise.
Found this guy a long time ago, good site
http://www.alansarchery.pwp.blueyond...eFrameOrig.htm