When I first got my ROBHS it was really froggy because I didn't understand the technique; I was just throwing myself backward. In a correctly performed BHS, when your hands hit the ground you're in a tight arch shape, and then as soon as they hit you snap off of them into a hollow. So you might want to think about that arch/hollow action instead of just trying to get over. You also need to have good turnover on your roundoff in order to have enough power to do a good BHS. At my gym we do a drill where we put a big squishy mat against the wall and do a roundoff off a panel mat right in front of it and slam to our backs. The idea is to hit your back off the wall and your feet on the floor at about the same time with almost straight legs and your arms against your ears so you're ready for the BHS. HTH!