I'm inclined to believe that the Rohloff operating demands are very different from single speed and VERY different from a tandem sync belt application, remebering that the Rohloff can generate some serious loads on that very small rear sprocket in its shorter climbing gears. A belt slip / ratcheting in that situation would be disconcerting.

As for the tandem sync belts, we had a couple belt slip / ratchet events with our very small diameter, experimental sprockets. In one instance the very high pulling load between the front & rear crank axles caused the eccentric to move and once the tension was reduced the belt began to slip. We retensioned the belt, used a bit more torque on the eccentric bolts and put a benchmark on the eccentric & eccentric shell to monitor eccentric rotation. The next time the belt slipped was under very, very heavy pedal loads on a very steep, short climb. After verifying the eccentric hadn't moved I was of the opinion that we probably induced enough frame deflection to cause the belt slip / ratchet.

Again, we were using 39t sprockets for our experimental system vs. the 70t (1st Gen) and 69t (2nd Gen) Gates sync drive sprockets: that's a world of difference in all regards. Well, that and our sprockets were CNC'd out of aluminum, not modeled out of polymers. In any event, our belt never gave any sign of being weaked or stressed.

Looking forward to hearing what the good folks at Gates have to offer.