I guess I'm proof that you don't need to be big to hit the ball far. I'm only 5-foot-9, 150 pounds, but last year on tour I averaged more than 290 yards off the tee. Distance happens as long as you set up properly and let your body just go, no matter your frame. It's not like I play recklessly. I hit 64 percent of my fairways, which helped me rank top 25 in a stat called Total Driving. The secret is to have two swings: one for power, one for control. The control swing comes in handy when a hole is tight or your timing happens to be a hair off. Owning two driver swings doesn't mean remembering a lot of technical stuff; I'll show you the minor adjustments that make it easy to alternate between the two. Practice them, then trust your gut to know which swing to bring.
When I'm looking to really bomb driver, like on a par 5 or reachable par 4, I tee the ball high and move it up in my stance, just off my left toe (1). A forward ball position naturally makes my body fall into a power setup. That means my head is well behind the ball (2) with the shaft leaning back and my right shoulder low. Keeping equal weight on both feet, I want to be wide in my stance (3). My torso feels loose, relaxed and prepared to hit the ball with an upward strike.
To hit a more conservative tee ball, I always choke down on the grip a full two inches (1) and narrow my stance so my feet are only slightly wider than my shoulders (2). I tee the ball lower and farther back, maybe three inches inside my left instep. This levels my shoulders more and helps me feel centered over the ball (3), like on an iron shot. One last thing I might check is that the shaft is basically straight up and down.
I like to draw the club back slow, but not so slow that there's any tension in my forearms. At the top, I want most of my weight shifted to my right side, maybe 70 or 80 percent (1). With the big shoulder turn I've made, my head has moved significantly behind the ball (2). From here, I feel I can just step on the gas. It's go time! How far back I move my head is a matter of timing that varies day to day. If I'm feeling super on, I shift back real far.
Because I was meticulous in my setup, I'm confident that the club has flowed back to the position I want it. Not having too much on your mind at this point in the swing is a good thing, so I won't give you much. Just like in the setup, I want to feel centered over the ball at the top (1). __Notice how my head has nudged only slightly back from address.__No more than 60 percent of my weight is on my right leg (2).
Up to now I've given you adjustments to make for power or control. Well, the downswing is easy because you want to do the same move for both. Even with the control drive, where you don't load up as much, you must swing down as aggressively as you would when you're going for full power. If you hang back, the tendency is to flip your arms at the ball. That's when shots go sideways. My lone thought coming down is, Keep the body moving forward (1). If you trust it and just whip all your weight to your left side (2), you'll drive it long and straight. At least most of the time.