I worked on this one a year ago, and made big improvments. (I went from driving the ball 220 - 270, if that is motivation).

The scouping issue that was mentioned above was my issue. I didn't believe it until I saw it on video. Me, scoup? NO WAY!

Here are two things that got me hitting through the ball.

1) Turn a screwdriver loose with your left hand, then both your hands as if on a club. This is the proper release motion. This is the only way your hands should move through impact if you are flipping.

2) Take swings with just your right hand as if trying to hit a tennis forehand. Now put your left hand on and make sure that the right hand passes over the top of the left hand and not underneath.