The scoop I've been using for Biggie's kibble, which I thought was 1/2 cup, is actually 1 cup. Oops.
So for the last 3 weeks I've been feeding Biggie 6 cups a day, thinking it was 3 cups, and worrying that he wasn't eating enough. Now I realize that he has been eating around 5 cups of kibble a day which is more than enough. No wonder he's so big. And no wonder he makes so much poop. Next vet trip tomorrow.