Fall for the small Field Maple

Fall in my modestly sized Field Maple (acer campestre).

I'm rebuilding the top third of the tree since last year.

Once potbound, and with maturing trees, Field maple hardly produces more than one healthy growth a year. This can be quite challenging en nerve wrecking if you need structural rebuilding at one point or even with refining. I'm quite sure the tree would benefit from alternating with growing conditions, changing from one year in big wooden container and a year in bonsai pot, when the purpose is still building it up.