For me, swinging feels like everything releases much later due to the automatic nature of the procedure. I don't get to both arms straight until well into follow through.
Actually, my feeling is that the right arm doesn't begin to straighten until after the ball. I must have been really messed up.
I agree that having more than one angel with you is good. Johnny Miller said he had three swings he could use: his own for a straight ball; Lee Trevino's for a fade; and, Chi Chi Rodriquez for a draw. He felt confident that one of those three would be playing good that day.
Actually, my feeling is that the right arm doesn't begin to straighten until after the ball.
To have an "on plane" right forearm at impact, the right elbow will be bent. Even Mo Norman with his outstretched arms had a bent right elbow at impact. How much depends on a lot of factors.
The key is that it is bent "just enough" to be on plane.
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Bagger
1-H "Because of questions of all kinds, reams of additional detail must be made available - but separately, and probably endlessly." Homer Kelly
To have an "on plane" right forearm at impact, the right elbow will be bent.
You are right, of course. But I didn't "own" a feel that leads to those correct alignments.
I believe I was having some serious downstroke sequencing problems (6-M-1) in that release was initiating before my arms, right elbow and left hand passed line-of-sight-to-the-ball (6-B-1-C).
So, I had book knowledge, but I had not translated it to a feel that leads that leads to ownership and ability to repeat the swing. The feel that the right arm doesn’t straighten until past the ball appears to have corrected that (for me).