just_lift, I go even parallel with heavier weights, the heavier weight helps me really beat the crap out of myself. I would recommend you only squat once a week, maybe twice if your on an upper/lower/off upper/lower/off/off type of split. IMO someof this has to do with how your long you legs are propotianetly to your body, and how your built. I have kinda long legs for the rest of my body, and it might all be in my head, but I feel its almost impossible for me to control the weight any lower than parallel. 6-8 rep sets for strenght 8-12 rep sets for size. Whichever you want.