oh yes, the ones I've listed are aggressive. Your choices are limited, but when you have 3+ inches of resident clowns, and introduce the 1" new clown, I'd think its fair. Resident clowns have the hometown advantage and size matters.
A long time ago, I had a tomato clown, then added 3 perculas. All were the same small size. The 3 peculas kicked the tomato out of its anemone, then forced it into the corner of the tank.
Currently, I have two 3"skunks, and I added 2 little 1" perculas. The only way I could do this was because I had an old 4" percula who offered sanctuary to the new commers. She was about to die and she did later but not before giving her territory to the new commers. Now all 4 clowns have their home.
If I was 2 add another pair of clowns... tough call. The coloration/markings would have to be completely different.
Oh wait a minute, schratch that. You can add more of the same species easily. They have a social hierarchy and pecking order.