Punishing is not going to help anything.
Get a second box. If it works, it is an easy fix and it also explains to you that the issue is a social one. You may find it easier to handle a second box than cleaning up the floor and then fighting with him over it - or not - but worth a try. If it doesn't work, it's only cost you $5 for a cheap one.
Has anything changed: diet/flavour of food, weight, eyesight, arthritis that might affect him wanting to go through that opening?
Last edited by SamIam; May 26th, 2011 at 01:53 PM.