Hey! I definitely would not crush an ume branch to bend it. I believe ume is slightly more likely to snap compared with other deciduous trees, but not much. You can bend young first year branches, I usually do that work in May. However, I would not try bending any ume branch that's over a year old and even then it's probably a better idea to graft in order to create a new branch. I did see a technique at Aichi-En, where one of the apprentices bent a 2-3 year old lignified branch down. He bent it to the point where the top of the branch which connects to the trunk started to tear, but it was just starting to tear. Cut paste was applied to the top of the branch and it lived. However, they explained to me that the process was risky and they probably would not have done this on expensive material. Better idea, but more time consuming option would have been to graft.