Spine angle will ultimately be determined by club length and the conditions of the lie of the ball. There is no easy way to explain this and each individual is built differently, so there is no one sure fire method to find it. In general "Balance" and the freedom to "Turn your Shoulders" are key here.
Yes, the more upright your spine is, the flatter the swing plane and vice versa..., but the more upright you can be, the easier it is to turn your shoulders. The shoulders can't turn very far when you're bent over. Does swing plane matter?... some, but not much. It will influence the club heads path and add some influence on the ball flight, but face angle is WAY more important... like 80%. It all depends on when the club face meets the ball... on the descent, or at the bottom. There is a spine angle that satisfies, the length of the club, and conditions of the lie of the ball and BALANCE... everyone has to experiment to find what works for them. HINT: You must feel once setup, that you are straight down to gravity! ... as if no one could move you in any direction... SOLID... not leaning in any one direction. The knees also play an important role to help adjust getting down to the ball and keep yourself in balance. This is what moves when I say "and sit down". A flatter swing plane is not the reason for blocked shots... the reason is ball position too far back and/or an open club face. A flatter swing will have the path more in-to-out, ... but with a square face at impact, you'll get straight or a slight draw depending on ball position. This is pretty heavy stuff to discuss and is unnecessary to know or digest, to have a repeatable, balanced swing. If you watch the Athletic Setup lesson video, I show you how to find the spine angle... hope this answered your questions Claude... Ross
Move Less ... Get Good! DUPLESSISGOLF