Too late to cut Hedges way back?

[Lawnguy6340]

I'm assuming the best time for this would be late winter/early spring, but am not sure. I've got an account with a Yopalm Holly about 11 ft tall that wants it down to about 5 ft. She doesn't was all the balls, just a big round puff. I told her the top will look bad for awhile and she doesn't mind. Is this a bad time to do it though? Could I be damaging the hedge by doing it as this time of year?

[PTLlandscapingIL]

id do it in early spring when everythign starts growing good again and the temps at nigth arent below freezing