Maybe I'll give it one more try a little tighter, since it's not been used/broken in the straps that fasten it may be allowing a lot of spring (don't know how to explain it right I'm sure) but if it gave and sagged down past his chest, then his chest didn't let it go back up. So a little tighter next time.
Ray it very well could be a bucking strap just the way it is, or a leg breaker strap, or a 'tripping' strap.
There is a very good retired saddlemaker just a mile or two from me who still does repairs. I was thinking if this strap showed any promise of being useful I might see about having dee rings added to the pad instead of fastening it to the cinch dees.
Thanks so much for your input.