This is great stuff, guys. Bumpy, you're right. It is a death move that causes all kind of over the top action coming down. I've worked diligently on moving my shoulder down plane during the downswing as well. One question--is C7 my upper vertebrae? Should I focus on moving my shoulder socket towards my vertebrae as I turn back?
You can simplify this by taking the tension out of your shoulders at address, and keeping it out on the BS.