Mach, you do great work!
But, I noticed you said you had defoliated it several times last summer. Now, I’m not the maple specialist, but if the tree were mine, I would have taken a different approach. Rather than defoliation, which I consider a “refinement technique”, I would have done repeated “grow out and cut backs”. The reason I would do it that way is the tree still has underdevloped primary branches. They need to build both girth and taper. In my opinion, tree is not ready for ramification yet. Defoliation creates smaller leaves and ramification, which isn’t necessary at this point.
I mean. The tree looks great! And you HAVE improved it a lot. I just think you can get to where you’re trying to go faster by not defoliating, and letting it do more growing, followed by cutting back.
Peter Tea gave a wonderful lecture to the Atlanta club about developing Tridents. He said that Tridents need to be developed in phases. Phase one is building the trunk. You definitely have that. Then Phase 2 is building the Primary branches. Phase 3 is building the secondary branches. Phase 4 is the ramification stage.
I see this tree as being in Phase 2. Building Primary branches. The “construction phases”, 1 thru 3, take a long time and are frustrating because everyone wants to get to Phase 4: ramification. Phase 4 is the easiest phase to accomplish, and that’s where defoliation helps. But to really build a quality tree, those earlier Phases must be completed first.
Peter told the story of his Trident that he owned before he went to Japan to study. He had it all ramified out. But, once he studied in Japan, he realized that his tree had inferior primary branch structure! When he returned to the US, he pretty much cut all the primary branches off to completely rebuild them using the “grow out, cut back” method, sacrificing years of ramification.