I had a referral to trim some Arborvitae that have gotten out of hand. These look fairly healthy but are over 8 foot tall. They are tucked away under some larger trees in the shade and are thin in the branches. The HO wants them cut to 4 feet. I don't think this is a wise move. My thought is to remove them and place something more suitable in the spot. The HO insists on them being trimmed. Can I safely perform what amounts to a topping of them? I would be cutting over 4 feet off the top. Thanks.