So I got a lesson recently and this was the core message and flaw of my old swing. I had too much pelvic tilt previously. After adjusting to this new stance, the results have been tremendous, however I've consistently been feeling discomfort in my middle back. It's nothing that impacts me during my play, but I was curious if there's any obvious reason why this would occur. For context, I'm focusing on keeping my hips in an extremely neutral position at address, and sometimes my thought is to tighen the core so that my back begins to arch in the middle of my spine, continuing to arch up through my shoulders.