Thanks, Evan. I got this a couple years ago and was drawn to its form more than the foliage (many J.maples are showier). So, the initial pruning was already in place and I have just kind of cleaned it up each spring, trying to keep the underlying structure visible. I understand this particular tree is very slow growing which is perfect in this placement. It came from my cousin's collection,
http://www.amazingmaples.net/ and he does a very nice job of shaping the trees.