There are entirely to many people who have attempted this and it failed. Clowns don't simply nip each other fins, they are down right nasty. They fight til one dies. They can grow up together, get along fine and then one day outa nowhere for no apparent reason they start fighting. So the "try it and see" advice is, IMO just plain cruel. If their odds were 50/50 or better then I could see it, but we are talking very rare instances that usually consist of odd circumstances where it actually works.
So, no. Don't mix clowns.