(Thread drift) Met you at George's in March and have been practising reeling silk and "opening and closing" by bowing the spine and using (trying) psoas muscles. Been getting a bit of back pain (small muscles spasming). Perhaps I'm being to eager BUT, hoping you might have some wisdom for me:-) See you again in August either way....
I blew out my back last year running and I'm still working through it. None of this stuff should hurt your back, but we've had a couple of guys who described the same kinds of problems - mainly because of trying to pull too hard with the back when turning. It may help to concentrate on releasing the musculature and letting the turn come out naturally (you may also find that you can actually turn further that way).