regarding lower back rounding at the bottom: looks like "butt wink" to me. can check out squat rx video about it, http://www.youtube.com/watch?v=Rq8CWv8UPAI, a similar youtube video by some other guy http://www.youtube.com/watch?v=QylNkkWBJUE. also on the SS wiki: http://startingstrength.wikia.com/wi..._Back_Rounding. hth