I don't claim to have success yet but I do have a juvenile emperor for about 2 months now. I got it when he was less than 2 inches but now he has more than doubled in size. I think the initial acclimating period is very important. I took half a day to drip the tank water into the plastic bag before I released him into a holding area in the tank ie roughly 5" by 5" by 5" enclosed by netting. I kept him there for a week, checking for any signs of disease on the fins and body and feeding him garlic soaked frozen brine and pellet food. I also installed a UV sterilizer. After I was quite satisfied that he is healthy, I released him into the tank at night. He hid for most of the time for the first two days (not surprisingly since he was the smallest fish around) but afterwards got bolder and swam out more and more. Now he is out all the time and has become bigger than some of the other fishes.
I know that I have not really quarantined the fish, nor have I kept it away from the other fishes for 3-4weeks, which is normally recommended. But my experience with new fish is that they normally would be down with all the symptoms by the first week, and if they can get past the first 1 or one and a half week, they would survive. Don't ask me why. I do have a QT but my experience with it has not been entirely good.
Anyway, that's my 2 cts worth