I have 2 pastels that just decided they wouldn't eat rats anymore. Nothing I could do would change their minds. They now has an addiction to ASF's. I am glad I can get ASF's (most of the time). They will eat mice but not very happily. I wouldn't give an 800g a rat pup. I would do a small. You don't want to get something too small for him.

Also some snakes just don't grow like others. I have 2 Mojos. They are on the same feeding schedule one (thank heavens the female) is HUGE. The male is small. I did have to start offering them different size of rats when the girl started to shoot ahead of the male but other than that, everything is the same.