I'm a 60 year old bassist, and my back is starting to act up. I've bought a bent endpin, but can't get the hang of using it. I like the basic concept, and it seems that I'll be able to reach the whole length of the fingerboard in a more natural way with less stress on my spine, but the bass feels unstable to me. When I stand with my normal straight pin, I contact the instrument on the back-right seam of the upper bout with my belly, and my left knee just touches a spot on the back. I can easily support the bass that way without touching it with my hands at all (this is a goal I've been giving students for years). When I use the bent pin, I can't reach the bass with my knee without doing something that seems really biomechanically unhealthy, and end up using my hand, or hands when playing pizz., to help keep the bass from "spinning". Any advice?