Finished the book on form and there was one more genius insight about arm movement - focus on moving them back not forwards. Genius because there is only one way you can do this, and there's a natural end. Whereas if you focused on moving them forwards there's a million ways of doing that, many of which are rubbish.
So for me the form thing is definitely working and I can already feel my calves easing up a bit, as the focus moves to quads, hams and glutes. Sadly these are a bit underdeveloped so some work to do - but will hopefully unlock more speed.