Good stuff Mark - I'm slammed this week, but I'll throw in that you might want to think about "tai no henko" - the "change of the body" which is usually represented by the circle (bamboo) and the interchange of fire and water, which are intimately connected to In and Yo, but are not (quite) synonymous.
Peter might have some thoughts....
LOL. Yeah. I started looking at tai sabaki awhile back. Thread is here:
There were some very interesting replies.
It just goes to show that when Ueshiba referenced anything "tai" or body, it wasn't about the physical, outward appearance. So, why would tai no henko be any different?
It's funny that we've copied the outward, physical appearance of tai no henko for over 40 years. It got us nowhere. And according to Aikido Journal, Ueshiba did this exercise regularly.
We obviously missed something.