In theory, the shoulder-driven stroke makes sense: It's like the pendulum of a clock. But in practice, it's not reliable. For one thing, the stroke gets too long on lag putts, which makes it harder to hit the ball flush. And when the shoulders dominate, the head tends to tilt to the right on the backstroke and to the left on the through-stroke (left). That changes the loft on the face, decreasing it going back and increasing it through impact. The result is poor contact and a lack of control. So putt with your arms, and you'll roll it with confidence.