Separating your hands into a split grip is a great drill to help you get rid of over the top. Hold the club like a hockey stick, and make some small swings hitting a ball. When you practice in this fashion, it will force your trail shoulder to get lower to the ground as you move through impact. Then, slowly work your trail hand up the shaft closer to your normal grip, while maintaining the feel of getting your trail side down toward the ground through the strike. The Split Grip Drill will help y