With them mounted above your head, they aren't going to keep you in your seat if your roll. Picture yourself upside down, your shoulders won't have anything restraining you from sliding up in your seat. I'm not even close to being an expert, but from what I've seen most guys run a horizontal bar behind the seat, that ties in with the b pillar. The harness should mounted at a slight angle, so as to force you back in your seat in the event of a roll.