midwestbonsai

Wow look at the trunk on that!
If it were mine, I would progessivly "chop" the tree down to the last couple of branches. And repeat throughout several years.
This will force the tree to produce buds further down the trunk, util they are at you desired hieght.
I have heard that Amur maple can/will die back after a branch chop, so make sure to leave a few inches infront of the disired chop location.
Hope this helps
-Paul