I've had a fair amount of success in going for S&V in the last few months. in the quest to the next level, I've been trying, as of late, to add more power and more kick to my serve. I do get some nice kickers with good pace, but still not on a fairly regular basis. I suppose what's going wrong is that I am keeping my center of gravity behind me for too long. I imagine this could be corrected with a stronger and faster "ab crunch" movement, which would move my center of gravity forward and closer to the hitting point. Is this a correct perception? Or, maybe, is the "crunch" in itslef, regardless of the center of gravity issue, a fundamental part of a powerful serve?