Mixing clowns is risky. Since the tank is so large however you can try adding in true percs on one end with an anemone present and you can also add two Sebaes on the other end to host another nem. If you don't want the nems that should make no difference for the fish. With such a large tank, as long as you introduce the fish to different ends, territorial disputes and other issues between the species may not occur. But it's never a definite thing...like I said, mixing clowns can be risky.