I'd agree with keeping a weight chart on him, but don't do that weekly- nothing changes that much in a week, & you'll only stress him too much, & if he's going to eat on his own for you, it's imperative that you minimize his handling & stress. I'd weigh him once a month, & do remember that retained wastes can make it appear to be a difference in the weight, as Beans already mentioned, so you might want to note when he eliminates also.