I would like to explain to you the plane of the golf swing. I think there has been a lot of misconception about what the plane is. I want to make one thing very clear, whatever plane you take the club back on, the club must come back down on that same plane; that is the only way the club can stay square.
Should You Swing on a Flatter Plane?
A lot of people say take it back on one-plane and drop it on a flatter plane, but the second you drop it on a flatter plane you have changed your radius, you have changed your arc and you can not square the club to the ball. There is no way that can be done; the backswing must always work on the same plane as the downswing.
How Does Height Affect Swing Plane?
What we have found is that a taller player will be on a steeper plane and a shorter player will be on a flatter plane, but the one thing we know for sure is that all players are on the plane between the rail the ball is on and the rail the feet are on. In other words a player of Jim Colbert or Ben Hogan's stature should be on the outer rail all the time.
A taller player such as Tom Wieskoff or even a Miller Barber or Jack Nicholas, who carry their right arms out a lot and take their clubs back with their right arms up and thus create a higher plane, will be on a little steeper plane. Jack Nicholas in his prime was always on the rail his feet were on and Hogan was always on the rail his ball was on. I can accept anything in between those rails.
Avoiding a Steep Rail
What you never want to do is be on a rail that is too steep, where the ball is behind you, then you really would be in trouble, and you never want to be on a rail flatter than the rail the ball is on. As long as you are in between the two rails, or on the rails, I don't think it affects you, but the key is to go up and down on the same rail; you can't drop it on a flatter rail.
Swing Plane Drill
One of the drills that I give my students to feel this is to go home and back up against a wall and take a practice swing. They take the club back and I show them that they will never hit the wall if they are on the correct plane. Most students, because they have been taught to take it back inside, will hit the wall on the first swing. You can see that if your backswing is too flat and out of plane you will hit the wall. So for this drill, find a wall that your wife will not see you hit, and work on taking the club back and up and not hitting the wall.