I do not think any of the coil overs on the market have enough adjustment in them to make belt tension an issue. Where I have seen this be an issue is with air ride and guys wanting to make a good amount of power. We've had them here at ZZP and if the air ride was not at the proper height, the belt would skip trying to do a power pull both on the dyno and the street. Initially we thought the belt was not adjusted properly so we set the height to stock and adjusted the belt. When left in that position there was no issue but once the sling was raised up or down from that position we would have issues under heavy loads. I've never had this issue with an non boosted sling however. I just don't think there is enough power being generated to skip the belt. But large changes in the geometry of the swing arm does have an effect on belt tension. What we ended up doing is having the owner set the ride height to their most common height and set it as a preset on the controller and adjust the belt to that height specifically. This helped circumnavigate the issue with the belt skipping under heavy loads.
Thanks... the person said they sent an email to your company... I just posted here because there is usually never a follow up by the person on FB regarding what they were told.