Hey there MTM, it sounds like you have a little chow hound there (the snake that is). I would think he could progress up to a small fuzzy mouse at that size you mentioned, and cut the feedings back to one every 6-7 days. I would start with a small fuzzy at first, not being able to see the snake it is a little difficult to say for sure.
As a very general rule, if you can't see a noticeable lump (and I don't mean hugely stretched) after he has eaten a pinky then he could easily go up in meal size. i.e. if you barely notice he has eaten, up the size slightly.
I hope that helps some.
Ohh, BTW, welcome! :wavey: