Top 4 reasons to set the right forearm and clubshaft on plane at address
 

1. It makes it easier to make crisp contact with the ball (avoid fat and thin shots). If you set the shaft plane below the plane you will be at impact, you have to come out of your posture to that degree. Maintaining your posture isn't good advice if you don't have the shaft and right forearm in-line at address.

2. It is also easier to strike the ball in the sweet spot if you are setting the shaft on the plane at which you will come through impact.

3. When the right forearm and club are mirroring your impact alignment at address it becomes easier to duplicate this alignment. Also, setting the right forearm and clubshaft on-plane can be done with some right elbow bend which moves the right shoulder down and makes it easier to avoid roundhousing.

4. Superb ballstrikers have done it: Ben Hogan, Moe Norman, Lee Trevino to name three.