I too have an over active right hand in the downswing. To determine if it's only your right hand that's the culprit, remove it from the club but allow it to ride palm down and open on top of the left thumb during a swing. It should remain in a passive state, but still provide some stabilization to the swing. My own swing behaves quite properly in this manner when viewed via slow motion cam. But, if you're quitting early on your rotation, the wrists are probably the first thing to go at impact.