if you cant plant the left foot, then maybe you need to work on the "fall" to the left. The whole body kind of "falls" to the left with the intention of falling so the left foot can get planted. Also, I believe one of peoples biggest reasons for a hard time with the transition is because of a faulty backswing, so you tallkiing about fault coil may be a very good observation.


as far as right shoulder down plane to start the downswing? I dont like it but it may work for some people. centrifigul force is an outward force from an inward pull, so if you move the left shoulder back, up, and in, then the club will go down out, and forward. Think of daly's left arm only swing.

your test results sound about right, when you post fromt he gound up the head should have moved back to about address position. is this where it moved to? If so you are doing it right.

swing may not get better overnight, but you have a couple of new understandings that you no longer have to worry about figuring out. Take notes of things you learn, keep a journal or something and reread it consistently. This is how you build YOUR swing

PS.
look into your set up, if that is wrong then the whole swing is in vain