Been stuck on this progression for a couple of months as well. I have made some progress on this but I still feel I'm way off. Using lots of lats and again I think thoracic may be an issue. AS you can see my top bar is out further than the video you demo on. Not sure if that matters at all. I have gone down and done C5 1/2 Hanging Leg Lift again. That didn't seem to make any difference on this progression.
Thanks again,
Cory