He should be on weanlings now, 2 small fuzzies are about equal to one small weanling. Get some weanlings and lay one next to him, its should be about 1.5 times the snakes fattest part.
Here is a good basic guideline to what to feed at their weight, but you can translate it loosely, such as if the weanling is too big let him gain a little more weight before moving him up.
Munson Plan