I have one in my 220g with no issues whatsoever. He's about 5 inches. I also have a 2 1/2 inch clown tang and again no issues. There were plenty at first but after I reacclimated the clown tang and then intervened in the hierarchy things have been fine. They've been together for a couple of months. The purple tang is boss of the tangs. The sohal doesn't bother any of the tank mates. My bluethroat pair and my green chromis don't take any lip from the sohal. It's a very peaceful tank let alone considering the stocking list. I feed four to five times a day and intervene with any aggression when necessary. I believe this has helped with curbing the aggression.
I also plan on upgrading to a much larger tank - in the 12 foot range. If, for some reason, I am not able to do so when the time comes, I have a number of friends with large enough systems to house the fish. This is something I took into consideration when I purchased the fish.