If his snake is over a year old it should be able to eat a rat that size, but you are right and that is why I also said depending on the size. I have a 200 gram 2yr old rtb that was underfed when I got her. She eats a 65 gram rat and leaves a little lump.
I have never heard a che being dangerous since it's only heat.
What or why have you heard that they are bad?