Since you asked...
I'd strongly suggest he stay away from in ceiling and if he must, go in wall where he can bring the fronts (at minimum) down closer to ear level AND more importantly, make it seem the tv/screen is the source.
My neighbor in Tennesse has a 12K sq/ft house. Main room has (I think) about 15' ceilings and they have ceiling speakers.
One day his wife scurries me in there saying "come & listen to our surround system"
Major let down.
Happened the news was playing. Voices were coming from above. It was basically like God was talking down to us telling us that it was going to be rain the next day.
Epic fail in my opinion.