Bumping this up with an update.
My gelding has gone from trying to bite anytime I touched his neck/shoulders to stretching forward, down and out during our sessions. Still doesn’t like it when I get deep in the shoulders though. I get a lot of releases along the underline/ribs. He spends more time standing square than he used to. He’s also standing wider with the hinds and he will now pick up his feet some instead of drag the toes. Topline, especially around the withers, is more consistent. The big one, last year the weather shift set him back and he went from standing solid to ants in the pants on the crossties. That hasn’t happened so far yet this year. Still very weak behind, but slowly improving.
Look at how square he got on his own.