Answer: You could do this, but do not do it now. The best time would be in late winter to early spring just before it begins to grow for the season. Then you will need to trim it back frequently to encourage it to branch and regrow thick and dense from the base upward.
In the meantime, you may be able to remove some of the oldest and longest branches to bring the size within bounds. Do not remove more than twentyfive percent of the branches at a time.
If you are growing these as a hedge, keep in mind that the overall shape of the hedge should be narrower at the top than at the bottom. This shape allows sun to reach the base of the plant. Otherwise, the top shades the bottom so much that it becomes leafless and bare. I hope this helps.
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