At seven months, I'd let him eat about as much as he wants. (As long as you don't go overboard, of course.)
Is he neutered yet? Neutered cats will grow slower so you can start cutting back on the amount of food you feed. 1 cup a day is probably good for now, I'd possibly try to scale back to 3/4 cups a day in a few months. (Try to feed three 1/3 portions a day if possible.) But it all depends on the size of your cat, too.