I'm wondering if seat choice and angle are the main driving factors in your shoulder pain?
The wisdom of the Internets is that shoulder pain generally means your seat needs to go back, I followed that and (my thinking is) closed up my hip angle and basically folded myself over, which was sub-optimal. Aero, but sub-optimal from a "make power" and "no pain" perspective.
If you were moving your saddle back, shouldn't you be lowering it too to maintain the same distance between saddle centre and the bb, and would this not also maintain hip angle?
The wisdom of the Internets is that shoulder pain generally means your seat needs to go back, I followed that and (my thinking is) closed up my hip angle and basically folded myself over, which was sub-optimal. Aero, but sub-optimal from a "make power" and "no pain" perspective.