Triggers are voracious eaters so they grow pretty fast., At least the ones I've had, did. I added a yellow tang to my tank that already has a red sea sailfin tang and a blond naso, and he was initially pick on by the sailfin, But they are the same species, Zebrasoma. This lasted about a week, but now all are happy. The naso didn't bother the yellow at all. I think you could add it ok. (JMO)
Oscar, You'll have better luck if the more aggressive fish is added last, in most cases. That's not to say that when it grows and becomes comfortable it might not become the tank boss, but it will usually tolerate the fish it grew up with.
Spring
j