[Andy R]

Besides the supporting role, at which points exactly MUST the right forearm also be on plane and at which points is it "allowed" to depart from being on plane, assuming it will not compromise its supporting roll ?

Thats a great question. Understanding exactly when the RF is on plane, when it diverges and realigns seems crucial for alignment golf.

I think many of us understand where it must be at times, but not all the time, and that incomplete understanding leads to fog/confusion.

Further, I think we would benefit from understanding 'RF alignment through the swing' of pro players whose RF's are not on plane with the shaft at address.