So it turns out that in the latest study, a heel-strike is actually more efficient for running. Meaning that the vibram-style shoes aren't doing anything healthy for you.
My hips tend to tuck under when the weight is heavy and I get fatigued. On the work sets, the first two reps are usually fine but then the butt will tuck under and by the last rep my upper and middle back might round too. I have no problem pulling the weight (or 20-30 pounds more) with some rounding, but I really struggle with a straight back and shoulder over (not in front) of the bar. I've noticed my ass tends to rise before the chest as well when I initiate the pull.
I've tried to take the weights down and building it up again with better form, but I start to round again at the same weights (which is about 20 pounds from my 5RM). It's not a mobility issue since I can back squat to parallel and front squat ATG with good form. My conventional DL is fine as well with no back rounding at all. Any suggestions for correcting it?