I've never stunned a rat either. As I have heard others mention, you get to know your invidual snakes and their body language. I can usually tell after the first few minutes who is going to eat and who is not. If one of my bps is shying away or just goes and curls up in it's hide, I just take out that rat and feed it to the next bp in line. Just don't leave rats in with your bp unsupervised for any extended period of time.