Posted: 09/10/2017 at 16:10
I've never grown acers, so this is very much a tentative suggestion, but working on the theory that 'growth follows the knife' would it be an idea to prune the left side of the tree harder than the right, hoping to stimulate stronger growth on the left to eventually rebalance the tree?
See here "...For most species, the harder a plant is pruned the more vigorously it will grow back. Light pruning will encourage slower but more branching growth. These principles can be used for many trees and shrubs to reshape an uneven specimen by cutting the weak side back hard but the stronger side lightly...." https://www.bto.org/volunteer-surveys/gbw/gardens-wildlife/gardening/pruning
What do the acer growers think?