My driver is 44½ inches, but I play it around 42. The driver is made for someone 6 feet tall, and I'm a lot shorter than that, so I grip down to compensate. But it also gives me more control off the tee because it's easier to square a shorter club.
Shorten the Backswing
The most important thing for me is to keep the club short of parallel at the top. If it gets long for me, I hit it all over the place because it's so hard to square it up at impact.
Sync Everything Up
The downswing starts from the ground up, but as I approach the ball, I want my body and arms turning together toward the target. Amateurs are usually all arms in the downswing, and pros often get the lower body too far ahead of the rest of the body. Syncing is a key to hitting drives that are powerful and straight.