Truball Sniper is a single caliper but does not have the web strap. you may want to look at some of the Scotts. The Scott with the NCS straps have the same strap as the TRUball and single caliper. I think their adjustment strap is superior to the TRUball. Instead of a very complicated buckle they have the strap through 2 bars that connect together with 2 hex screws. They also have a rope system instead of the strap.

I posted before seeing what TFOX posted. Sorry. the little Bitty Goose is probably the the best choice in my eyes. The one side pivots a little which should help alleviate torque on the string.