Yeah, I don't exactly know why I do that. I think the twisting comes from trying to clear the shirt with my support hand--I have short arms and a long torso so I have to twist a bit to reach. And based on the class I took earlier this year I think I might also be doing it a bit from a subconscious "keep the gun away from the assailant" move.
The hunching, no idea. Not intending to do it; probably trying to not be leaning back.
I'll work on some of the stance stuff with the laser trainer tonight or tomorrow and see if I can get myself a little straighter. Then I'll work on drawing later in the week.
Thanks again, everyone, for the feedback!