Y'all have spare belts on hand, right???

I only ask because that's the one thing that I've looked at as the limiting feature of belts for off-road tandems: the ability to deal with ingesting nature between the belt and sprocket without damaging the carbon fiber strands inside the belt.

Getting a stick or other debris picked-up and sucked into the sync drive on a road tandem is a fairly rare occurance. However, on Off road single track here in the heavily wooded places we ride it's not at all that uncommon to ingest a branch and see it quickly chewed up by the chain & rear ring teeth or to simply have the rear chain either get derailled or moved a few teeth and end up out of sync.

So, looking once again at the special handling instructions on the belt and how a bend, kink or the act of hyper-extending the belt such as by rolling one on or off a sprocket vs. loosening the eccentric I would be inclined to keep an eye on the section that ingested debris just to make sure there aren't any signs that the core may have been damaged.