I know how you feel about being antsy feeding live rats versus mice. They're a lot bigger and very much more vocal - the bruxing ( teeth chattering ) definitely makes me feel at edge especially when they do it in the feeding bin with my snakes. I started mine on barely weanlings, working my way up to a small rat. My routine: always be present, always have tongs in hand - ready to bop the rat on head or to uses it to keep them from gnawing at the snake once they're constricted. Also, rats don't smell like rats do and some say that plays into how eager the snake will strike. But From personal experience, my mouser will not eat a rat if it doesn't smell like a mouse. My ratter doesn't care. If you do have a problem feeding a rat to a promising mouser and only have rats to feed, try scenting your feeder rat with aspen scented with mice. Just take some aspen the mice have used and rub it on feeder rat. Again, this is just what I do and it works for my snakes. In the end, your snakes will tell you what it wants to eat, when it wants to and how. But part of the hobby is being patient. Good luck!