Is Hexapuma enough larger than the other cats that you can take a cardboard box and cut a small door into it that the other cats can fit through and he can not?

Hmm... Hex is still smaller than Mozart, though he may eventually (like, next Wednesday) surpass him in fact if not in deed. Scrabble is your basic seven-pound Cat's Cat. It's Scrabble who is most traumatized by the Tiger in the Kitchen, but I'm not sanguine regarding the probability of her willingly entering a box, even to eat. Worth a try, I guess. At the least it will be amusing watching Hex pushing the box around the kitchen, with his head stuck in the opening...