Snakes will grow slower if you feed them less. I've seen this personally in young snakes, but not on purpose. In fact, sometimes growing slower is better for the snake than growing as fast as they can. This will not, however, affect their evenutal adult size. Feeding them so little that they don't reach their potential is wrong. Also, a very underfed snake will become aggressive.I know this sounds vague, but the actual amount differs from species to species. Maybe you could feed a decent sized meal every two weeks or something like that. None of this is really red-tail specific, I don't have one of those... yet :).