the newest development is trying to change the previously taught mechanics of the SH. Instead of the lean back, with the hock/stifle angle remaining open, I am looking for a truer bend of the haunches. Simply put, the straight line from hip to the hoof becomes shorter. Right now, it's more of a lean back/lower haunch - kind of like the hip moving on a semicircle back and down.
The strategy for this is to install a new cue: hand push on the croup to lower.
We played with it for the first time yesterday and this is how it went:
in our old SH place, I put my two fingers on the highest point of the croup and slightly pressed down. Then I added a whip tap just in front of my fingers. Released both when he offered a slight movement downward (and back as well). After about 3 times, he responded from the finger pressure alone. Next I began to shape the response a bit further, when I would sort of resist the croup moving backwards, just guide it straight down. And it worked! What an incredibly clever horse!
It's pretty hard to see from this close to him, so I will have to get it on video asap, but I think this is a viable strategy. I also add a verbal cue of "sit" just before asking for this new way of SH. The possibilities from here are so exciting! yay