The Everman belt drive system (aka “Positioner utilizing engaged toothed gear belts, one static and one dynamic”) is a simple modification that reduces the stretch or flex of a timing belt over long drive systems.

When used with V-slot it simply involves securing by glue or tape a length of timing belt inside slot with the teeth up. This lines the slot with a grooved track (similar to a rack and pinion drive) that the drive timing belt fits into.