[BerntR]

While look-look-looking I just realized that the shaft will rotate some 90 degrees from top to impact. As I realized that I suddenly lost all arguments for puring and/or spining.

Anyone able to defend puring and/or spining even considering the shaft rotation?

Interesting question that I haven't thought much about.

Let me suggest a few points to consider.

Assume a perfect swing with angled hinging and pure rope handling. Then there will only be centripetal force (from the head upon the shaft) that will bend the shaft. Because the cog of the clubhead is above and behind the shaft (as seen from impact) the bending force wil be downward and forward when the shaft is loaded and it will unload upwards and backwards.

With a perfect hit, things gets more complicated. Centripetal force will still do it's thing. In addition, drive loading will induce a clockwise torque on the shaft as well as a backwards bending in the loading sequence and and in the opposite directions as the club unloads.

Then there's of course what happens in the moment of truth - from impact to separation. I don't know if spining has any part here.

Finally, real life swings might be somwhere inbetween - like swing with a strong extencior action through impact. And imperfect pp alignments.