Mike's question led to a long and winding discourse that never came back to the point of raising the arms from the center and two years later, that point has never been fully addressed.
So how about it, Mike?
Is the experience described above related to what you meant? Can you expound further on how to raise the arms "from the center?"
I dunno, David. I tried to briefly describe something to an old friend of mine yesterday (he's a longterm student of Ikeda Sensei) and then I went to describe the same thing in person to a couple of other people this afternoon and I had this realization again that it's almost impossible to describe these things in writing. In person, I had to keep backing up to clarify and show a point, so I suddenly realized that my written description to an old friend was pretty much useless.
Essentially, I don't want to touch your guesses about the connections,etc., to the hands from the hara unless I can feel what you're doing in conjunction with the way you're verbalizing it. That's a safety to keep me from misleading you by agreeing or disagreeing with something you've said. "Jin" is the foothold knowledge. One you understand up-jin and down-jin (the ki of earth and the ki of heaven), everything else is a logical progression.
When you raise your hands, the hands ARE the dantien; when you lower your hands, the hands ARE the crotch-weight/hara. Remember how our friend Justin Smith had fun with the crotch-weight idea because he didn't understand the physical principles so he thought it was some sort of spurious remark.
However, the connections (fascia and jin) are something that is impossible to say in words.