IMO Jam, to go back half way, the shoulders would need to rotate 45° in order for the left forearm to get back comfortably to horizontal.
As for the wrist cock, all I'd suggest is that you try it with and without and see what works best for you...
The Pelz Short Game Tips section of his website have been of immense value to me. For me, the critical thing has been committing to a full follow through on pitch shots and only varying the length of the back swing in order to vary distance.
I am far more confident inside 100m now than I was when I first joined GTO last year.
Good luck with it.
Cheers
