I agree totally with MT79. The larger the maroon clown, the meaner it is. Thinking I had enought room, I tried 2 percs and a gold striped maroon in my 180 g. All about the same size (maybe an 1 1/2 - 2 inch in size). Everytime a perc was anywhere near the maroon, it got chased away. After realizing how mean the maroon clown was I removed the percs. I don't know if the maroon would have necessarily killed the percs, or even damaged them for that matter, but i didn't want to chance it.
If you want to try to keep 2 species together, I have heard that some have been successful in mixing and matching clarkiis, percs, and skunk clowns.
Or you could just mix oscellaris and percs; they will definitely get along. HTH