I currently have a maple I purchased about 8 years ago. It is now about 40cm in height with a trunk circumference of about 7.5cm. From the soil to the first branch is about 20cm with what I believe to be a graft scar at about 10cm. I have only ever cut the roots and branches twice (in alternating seasons) to keep it in the same pot (d=30cm h=35cm). I think I would like to chop the trunk to begin to create a formal or informal upright that would be 15-30 cm in height. I would like your opinion if now would be a good time to do this or should I wait and concentrate on surface root formation (currently all roots are under the soil)? I am unable to plant it in the ground but I can plant it in a much larger pot (about twice the size of the one it is in now). Any other comments or suggestions are also greatly appreciated.

Thank you for your time.
Paul