I have just had to rehome a PJ tang, very simular to the Sohal! I thought i would get away with the agression issues in my 360g system with a hippo tang, lipstick and a sailfin. No chance!
The PJ i bought as the smallest tang because of their attitude, up untill about 6months ago the PJ tang was so laid back and placid, then started chasing the others just a little more weekk by week.
I have had the fish for two years but it came to a point where the tank would just be so much more peacefull without him, and at only 6.5" he would only have got worse. Though i was sorry to see him go as he was a stunning specimen.
Since he has gone all my other tangs are swimming around and on show much more, and the whole tank just feels more peacefull.
I think these fish, size issues aside belong in aggressive fish only set ups, they really need tank mates like triggers etc to keep them in line!
The Sohal is a very simular fish.
Just my 2cents, but bare it in mind!
Regards
Mark