My flame angel murdered my clarkii clown in a 180 - and the clown was well able to put up a fight. It started off as the ocasional squabble. It then became more frequent and a little more serious, though it wasn't that bad. One day I noticed that the clown would not leave the sacrophyton mushroom that he can come to think of as his anemone - and the flame looked very tatty around the edges...... on closer inspection, the clown had an injured eye, and later died as a result of infection.
The flame was definitely the agressor in all cases, and being a good match for one another, the flame just would not let it rest. I would think that a cherub would be more of a thorn in the side than a clarkii clown, and seenig as the tank is half the size of my 180 then I would advise against it.
My friend now has the flame in a 150, along with a large maroon clown - much larger than the flame, and very well established...... the flame is at his old tricks again, and my friend is now going to have to break down his tank to get him out (this flame is too smart for fish traps...... he has a 6th sense!!!)
HTH
Matt