I don't know much about these matters, but it sounds to me as if the problem is not the strap, but maybe your shoulder. If something you've been doing for fifty years without a problem suddenly starts causing pain, maybe you should have the doc look at it.

A short-term solution might be another style of strap -- I think there are ones that just go around the neck and somehow loop underneath the body of the guitar and hook into the sound hole. I've never tried one but I'm pretty sure I'm not making it up. Maybe one of Mudcat's hotshot pickers will know more.

McGrath, Irish bands sit, Bluegrass bands stand. It's just the way it is. You're right about standing for 50 years, though!

Cheers, Nancy