I have no useful suggestions whatsoever, but I thought I would post a very old stump I dug up from my new house. It was a large overgrown mess falling into the driveway when I bought the house in late 2008. I cut it back and wrestled it out of the ground in early 2009. I left all the trunk stumps too long originally; I do not pretend to have a credible explanation for this, although I must have had some sort of thought about that at the time
In any case, it grew quite happily last year, and I cut the stumps back again this winter This is where I am now. Some of the live stumps still probably are too long, and a lot of the stumps you see are dead but, I think, beautiful. The eventual plan is to try to save the bases of most of the stumps and to thicken up new leaders and to give them movement over time, eventually settling into a nice clump style.
It even flowered for me this year, in its first year in captivity...I think that's good. I think.