It's definitely okay. Like the poster above said, if you're worried about it, just allow him a few extra days to digest. When I fed my cinny that larger rat, I actually didn't give him any extra time between meals because I believe if your snake doesn't want to eat, he won't eat but my cinny is a little pig so he didn't miss a step the next feeding day even though he had a bigger one the time before. If your snake takes the rat, the only reason you should worry that it was too big is if he regurges. Otherwise he'll be fine.