I've started training this maple about 3 years ago. It was a grafted cultivar. First season I ground layered it. The second season of having it, I put it on a board. No nails to spread out roots, just screwed to a board and left to grow. Third season, I skipped work. Just too busy with things, but I managed to get two airlayers off the top. One I split into two and grafted to my root over rock. Going on 4th year now. I did rootwork, cutting away about 4 large roots. Fortunately there were still a good amount of small roots all way around. I nailed some roots to spread them out better. Not a lot. If I had some small rooted cuttings or airlayers, I would've put in some thread grafts to get me ready for the next chop. It needs a new leader and a few branches. Trunk is about 2 inches.