Although I agree with you in general, each fish is different, I haven't had any aggression issues with my yellow tang and truncatus bristletooth in a 3'x2'x2', so in the end it depends on your specific fish. Some Ctenochaetus are definitely a lot worse than others, a striatus is the devil incarnate. I've had the yellow tang around 3 years now, and the truncatus I caught locally on our East coast by Durban harbour around 2.5 years ago. I would also suggest a yellow tang and scopas would reach the same theoretical maximum size as they are basically the same species genetically.
As an aside, I also have a regal tang in there which I also added when small, it is terrified of the fish trap, have been trying to remove it for over a year. Moral of the story is that it is a lot tougher to remove a fish than it is to add one, so have to think twice before adding anything you plan to remove again one day. It also does not seem to be too stressed, the foxface is most nervous out of all of them for some reason. A pic of the tangs and tank attached as reference (the second foxface in the pic was removed a few months ago):