backroll need help

I've been trying a backroll the last 2 times out and have been having some trouble. When I come my closest I come all the way around and come down the opposite wake but then my board just slips right out from under me. I believe it's due to momentum and I just keep rotating. So i guess I'm asking how do I stop rotating and just come down straight?

I watched Detention and it looks like he moves the handle to his front hip, will this help? Any input will help, thanks