Like anything in golf, there are many factors that can affect any number of things in your swing. If I told you that your grip or ball position affects your swing plane would you believe me? Well they do, as well as alignment, weight distribution, weight shift and hoards of other factors, but for players who really struggle with coming over the top and hitting a wicked slice or pull hook, I think more thought needs to go into what plane their shoulders are moving on during the back swing and even more importantly, the down swing.
The first golf lesson I ever took from a top named professional was from Michael Hebron who was PGA National Teacher of the Year in the early 90s. His shtick at the time was “the inside moves the outside”, basically saying that your core and big muscles move your arms and hands and small muscles. He loved to say “the dog wags the tail”, rather than “the tail wags the dog”. Makes sense right, but what does it mean for you? If you are a slicer or pull hooker it should mean a lot. Wherever your shoulders go, your arms an thus the club will go. If you start your downswing while spinning your shoulders open before your arms have had a chance to drop on plane, your only choice is to swing over the top of the plane.
Try keeping your back at the target longer while your arms have a chance to start dropping down on plane. Don’t be in such a rush from the top to get the swing over with. This particular swing plane issue is not a position issue, but rather a sequence issue. Get the arms down on plane and then worry about turning towards the target. If this is a big problem for you over exaggerate it until you start striking the ball from the inside and starting it out to the right of your target. You would be well served to even feel like your shoulders are closed to your target line at impact. The biggest problem I see with golfers who chronically come over the top is that they don’t over correct enough. Go a little crazy, exaggerate, have some fun and I think you will be surprised at the results.