I love my six line! it has the most character out of the any other fish in the tank, except maybe my watchman goby.
It is true however, mine can have an attitude to anything it decides to have one with, including me! I was looking at the six line close to the glass one day and it flashed itself and all fins erect starting shaking at me ha ha. other than that, it has picked on my smaller clown but i have an anemone for it, so its OK. my royal gramma is bigger than the 6 line, so that's OK, and my goby hides.
i think you'll love your new fish!