Repotting young cultivars of maples

I recently received 2 cultivars of Japanese maples-a 3 and a 4 y graft.

They are in what looks like an organic containing soil in 4 in X 4 in X 4 in containers, are healthy, and growing at my zone 7 location.I just trunk chopped both to fit in my greenhouse (18″ high shelf to shelf) and wish to repot or slip pot them into bonsai pots.

Is now a good time to do this? My soil of choice is 70% akadama mixed with 30% pumice.

Hi Joel - if you repot now I’d go easy and leave most of the existing soil in the rootball. If you wait until early spring (just as the buds start to swell) you can bare-root the trees and plant them in the new mix.