Never had a multibarred long enough to comment on it. I added a male Venustus in 11/09 to the DT with male Coral Beauty (10/09) and 3 Flame angels (10/07). The Venustus will not engage with the CB which is the trouble maker and the Flame angels ignore him.
I would highly recommend QT the Venustus and allow it to learn to eat prepared food before adding to the DT. I don't see any problem with either choice (especially in a 270) as long as it's eating first and you've plenty of hiding places.
GL