I just saw some video of my throw, and I noticed I turn my shoulders past 180 degrees (significantly past) in my reachback. I'm thinking this is not good, because when I look at videos of pros they only go ~180 degrees back. it might explain my occasional pulling to the left (LHBH). I'll try to illustrate it.
mine:
__/ (mine might even have a little more angle)
Pros:
__|
(the horizontal line is the arm in it's reachback)



