Dog food measurements.

 Overfeeding: he'll look fat. Sorry, [lol] I couldn't resist. Seriously, if you overfeed at lot all at once, you'll get soft serve poop. After that, the body adjusts (sometimes) and the dog gains substantial weight.

Underfeeding: dry skin, dull coat, lack of energy, and of course body condition score goes down - ie, you can palpate hips and spine easily if that's not right for your breed.

Rivers's is the same way; drops weight at the slightest drop of food portions; I believe it's just his breed and metabolism.

If I try to up his food at all; it just revisits my yard in a stinky slimey mess!

 Wow... FOUR cups a day ? How much does this dog weigh ? My 70 lb very active lab gets 3C of TOTW a day w/a tablespoon of canned or 1 Nature's Variety raw medallion. My 80 lb GSP who is inactive gets 2C of TOTW w/the same mix ins and on a better quality, higher calorie food they get even LESS.  4 cups seems like an awful lot of food unless your dog is in the 80-100 lb range considering that you should always feed about 25% LESS than the amount recommended by the manufacturer for the dog's ideal weight.

If I feed them any raw the same day the kibble gets cut way back.

 Joker weighs 45lbs. And he is a very active dog. Different dogs require different food requirements regardless of the breed and weight.