Pete,
I stump shoot alot, when I clip it to my belt loop and bend over to pick up an arrow it pops off my shoulder. I often wear a lumbar pack and a binocular pouch in the front. When I would have it loose enough to fit around these it would flop off my oppisite shoulder when bending over. I was always trying every adjustment I could think of (granted my thinking process is somewhat limited) but I was still a little frustrated. This took care of the issues for me, as they say, your milage may vary.
All the best, Terry K.