The attached shows using the tape transport guides from an old portable video camera to take out the play (backlash) from the belts. One carefully positioned hole is all that is required. The transport guide is perfect - free running bearing very round and 8mm deep, the belt is 6mm. It pushes in to its drilled hole after the belt is fitted. The only caution, it must not hit the main casting when gears are meshed. Contact me if more info required.