On both the trunk chop questions the answer would be yes, it can be done.

I have a F. benjamina that I found on the refuge heap that was just a
stick with all it's top branches cut off, and with no soil remaining.
Obviously it had been discarded by someone who did not want it as a
houseplant anymore, and had not been lying there for more than a day or two
when I found it. I put it in water, and it sprout new leaves in about
three
weeks. Based on this and my experience with other Ficus sp., I would say a
total trunk chop would be fine as long as the roots are not disturbed.

Regarding the Celtis sp., I've trunk chopped many before, and as long as
they get enough water, there is no problem with resprouting. Keep pinching
the new leaves to reduce leave size, unless you are growing new branches for
thickness, which will be chopped later.

The best time is really up to you. It depends on your aim and
expectations.
If you do it during the winter, the new leaves will be large with long
internodes, and conversely, during summertime the new leaves should be
small
with short internodes. This being due to the winter stores of sugars, etc
in the roots. If you also chop the roots at the same time, and the tree
survives, you should get small leaves and short internodes regardless of
season.

Renier van Rensburg
Cape Town, South Africa

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