[Jeff]

I personally think that Tom Watson's advice on turning the shoulders perpendicularly around the spine is good advice, but that doesn't mean that the the shoulders will turn on the same angle in the downswing as it turned in the backswing - because the spine angle shouldn't remain the same in the downswing. In the downswing, the pelvis shifts left-laterally and that causes the spine to develop increased rightwards spinal tilt (secondary axis tilt). That will cause the right shoulder to move downplane, and rotate less horizontally, in the downswing - compared to the backswing.

Robert Baker demonstrates that point in this swing video lesson.

http://www.golf.com/golf/video/artic...595277,00.html

Note how both Tiger Woods and Ernie Els move their right shoulder downplane in the early downswing.

The following photo shows how the right shoulder moves along the upper hula hoop path, which has a changed axis due to increased rightwards spinal tilt.



Jeff.