I don't use climbers but when I'm setting up my hang on's I'm always strapped in. I use a rock climbing harness and 'beaner and static rope. I figure if it works at a couple thousand feet it will work at 20'. As a few have mentioned the "pain" of moving the strap is nothing compared to a lifetime of pain, or death.

Just out of curiosity BobCo19-65how do you use an ascender if a rope isn't already up in the tree?