[Mike O]

Mike 0 - Just to tie off our discussion because I agree it has run its course - here's the formula and example:

Centripetal Force example
F=m(v^2)/r
m=mass of clubhead (200g for a typical driver)
v=velocity of clubhead (let's assume 100 mph @ impact)
r=radius of curvature of clubhead motion (shaft length is a good approximation, but it could be slightly longer, let's try 45")
Anyway, then F=79 pounds force for this impact condition. The force is considerably less at other points in the swing.

There's a table with similar calcs here plus more discussion on shaft bending.

The second paragraph I quoted I think you have it right. Yes the shaft could bend forward and the sweetspot still not be even with the shaft. In fact, according to some, having the CofG inline with the shaft is the maximum condition that can occur but is not always fully achieved. There is some twisting going on too but I have to assume that it's not the biggest effect - otherwise we'd all be hooking our large headed drivers off the planet and most people tend to have more trouble getting the larger heads around.

thanks- some very good points!