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 might even have a little more angle)
(the horizontal line is the arm in it's reachback)
Being overcommitted and greedy often leads me to turn my body early putting the left side in the way of the disc. I've got a bruise i did to myself on last Wednesday. Ouch. Turning more than 180 adds power and reduces accuracy and repeatability at least until you get accustomed to the form change and probably a little after that too. I think on average i gain about 10-13' from reaching back 190-200 degrees vs 180. I don't usually do more than 180 unless there is a lot of open space and there is a chance of shaving a stroke off the score.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.