Step 1: Adjust Your Setup
Since your goal is to use vertical force and launch upward through impact, add some knee flex at address. You can't shoot skyward if your legs are already straight! And since your right hand likes to push down on the ball, set it on top of the grip in a traditionally "weak" position. It won't feel weak when the ball explodes off the clubface.
Step 2: Go to Launch
Set up for the lower-body differential screen again, this time with your hands pressed together in a mock address position. Swing back. Your goal? Smack the pad, just as in the drill. As you start down from the top, however, pressure your left knee in the direction of the ball of your left foot. This pre-sets your launch. Then, spin around your left leg, allowing it to straighten (launch) as you deliver your hands to the pad with a mighty "thwack."
Step 3: Pre-set Your Power Source
Flexing your knees at address is a good way to position your lower body for an upward launch. Take it a step further by increasing the flex in your left knee as you swing the club to the top. It may look funny, but you'll definitely feel like you're pressuring the ground for a massive strike.
Swing Thought: Raise Your Buckle
As you start down, think of your belt buckle. If you launch correctly, you'll feel it move several inches higher from its position at the top to its position at impact. The trick is to thrust upward while maintaining your original spine angle. Focusing on your belt buckle helps.
Special thanks to instruction model and PGA teaching professional George Wrede.