[6bmike]

I just read 2-F a dozen times, seemingly for the very first time (although I know better.)

The plane is the inclined angle that the clubshaft forms when properly soled.
It is recommended that the right forearm be postioned at the very same angle and remain on the same inclined plane throughout. Is the sweetspot plane then another line emminating from the sweetspot rather than the hosel? Just read 2-N-O a dozen times, seemingly for the first time. The References to the "sweetspot plane" are all over the place! I fear I have missed something really important. That yellow book has reduced me to a blubbering mess yet again! If inclined, please break this to me sweetly. Cringing for a potential bludgeoning.

The shaft is a proxie, as young Lynn explained it. It subs for the sweetspot plane because it is attached to the clubhead but when push comes to shove, it is the sweetspot plane that we "swing." The shaft rotates around the sweet spot. Make a quick model with string and scotch tape and check it out.
When you see pictures of the clubhead racing ahead of the shaft to impact- that is the clubhead and the sweetspot plane inline.