[Mathew]

So to build a swing around this zero shift plane is okay, but that is a different plane than the shaft plane? If so, different but parallel? or just different?

What I am saying is that the zero shift turned shoulder plane is an ideal. The closer one may become to that ideal the better from a pure mechanical perspective. However alot of golf clubs make it nessesary to be on a different plane than that of the turned shoulder plane at impact. Also a golfer is not as exact as a vector geometrical model I can draw. The main thing is to be 'reasonably close'.

Also, the shaft rotates around the sweetspot. The line of the longitundinal center of gravity stays on plane (which basically is a straight line from the butt end of the club to the sweetspot). The golf club is an instrument in which you weild its mass (clubhead) in space not the medium in which you connect with that mass(clubshaft). You draw a straight plane line with the sweetspot, not the clubshaft.