I think I'm going to need someone to physically move my body into position to reflect that change in my shoulders because I think what I'm doing is so burned into my muscle memory that it doesn't want to go anywhere else.

For 3D shooting I always liked that slightly "aggressive" posture of going to the shot and being able to stay behind everything fully by setting up just a tad short. That's where the slight chin down comes from, and I hate that feeling of being out of pull and too stretched out, that's when things fall apart for me so I like to be sure I will never find myself in that stretched out leanback posture trying to find my angled shots. A touch short also allows me to feel stronger over the course of 30 or 40 targets in up and down terrain. The back doesn't seem to get as fatigued.