Gates has belt tension parameters at their website and if I recall, from my time owning a R&M Charger with the Nuvinci, that if the belt is too tight that it can damage or reduce the life of the IGH. Perhaps that is something you might want to research as my reading on the subject is a couple of years old. As for the drag, that isn't something I recognize as a belt problem but sounds more like it would be attributable either to the Bosch motor or the hub.