My starcki would have been the boss and lorded over the entire tank if he was the largest fish. Stacki may be peaceful for damsels, but they're still damsels... don't forget that.
Since my Potter's Angel wouldn't let the stacki push him around he sort of gave up on lording over everybody. After a few weeks he finally decided on a cave he liked and it was HIS, no other fish was ever permitted inside it again after that. But he generally was peaceful regarding the rest of the tank as long as they stayed away from his spot.
So I don't think you have to add him last but I'd make sure there is at least one other fish in there that can hold it's own first. They are more semi-aggressive than peaceful in my book... he never did actually hurt anybody though.