I have a Panther. Was about 5 inches four months ago, now he is pushing 9 inches. Easily the largest fish I have. Anything under 6 inches I would not recommend to place with this fish. I had a molly in my tank when I first got him, the molly was about 3 inches and still the grouper tried to eat him. Your perc will be lunch.
If it were me, I would chose the Panther over the clown, but that is just me.