Don't worry lol. He's not much of a cardboard chewer but it might be worth a try. Currently he is out nibbling his hanging chew stick
though I have laid it flat inside his large rat tube as it catches all the bits that comes off and isn't as noisy as when hanging from the bars. Will be thinking of you. Hope you and little Charlie get sorted he's so cute. I loved the photos of your vet outing whole waiting for the taxi