Does the belt fit easily between the sides of the V-track? In the photos, it looks to be too wide. I have to agree with the others suggesting solid wheels. That will spread the pressure across the belt better. You can see how much it is flexing between the points of the V-wheels.
The new belt does @ 5mm width We noticed this happening on the old 6mm wide belt and moved to cut a half millimeter off on each side and this leaves room for the belt to lay in the track with out any obstructions.
The model located in the Files tab above for this build, has been updated with the OpenBuilds Solid V Wheels This system works awesome with these
With a belt slicing machine Well really our manufacturer does it for us on these special order belts.
Coming in late.. Maybe just an observation but the original concept looks to have 2 differences... One: The idler pulleys on kram242 seem to be further apart and closer in the Z direction; having the end effect that the belt is at a 45 degree angle as opposed to the nearly 90 degree angle seen in Robert's example picture. This would have a < 160 degree wrap on the pinion and less than 90 degree contact area on the idlers. Perhaps this results in less friction and wear? Two: The original example of the double v-wheel would seem to eliminate (or minimize) the drifting of the belt from side-to-side.