I personally house 7 tangs. 3 acanthurus. (Achilles, PBT and a Powder Brown.)
@4FordFamily is going to be better on this than me. My Achilles and Powder brown went in together. 7 Months ago. Added the Powder blue about 5-6weeks ago. Mine all get along very well. They gripe a bit here and there but nothing that results in damage. I do also have a Kole, and three zebras, desjardini, PT, YT. My sailfin is the largest of all of them 5.5"+ and he keeps everyone in check.
I really wanted a Clown Tang and 4ford advised me not to add one with an achilles. My powder blue is the smallest of my group at around 3". He is bold and if he begins to be problematic as he grows I will remove him.
Jason and I both thought my powder brown was going to be the problem, he was a major jerk in QT but is way lax in DT.
The most aggression in my tank is between the Purple Tang and Yellow tang believe it or not. They were QT'd together and introduced to Display together.
Tips: Always make sure to have enough nori on a clip for them to graze 3/4 of the day.
If you want to add other acan tangs, get them into QT with your current fish as success is much more likely with DT introduction at the same time. Or at least in batches of 3.
If you aren't introducing them together an acclimation box is probably necessary to stand a chance.
IMO a lot of it just depends on the temperament of the individual fish itself, but the above pointers increase the likelihood of a good atmosphere.