I have some neonate rosys that were born in the begining of Sept. that are already eating Peach fuzz pinkies. This has not been any issue with size of the peach fuzz mice,regurge, or anything else. I have always gone off to feed most all snakes a feeder just a little larger than their biggest part of their body. You should see a little bit of a lump even when the food is at least half way down their body.
Here is the feeding regiment that I use.

Neonate
1 pinkie mouse or small fuzzy mouse
Every 3-4 days

Juvenile (1 yr)
2 fuzzy mice or pinkie rats
Every 4-5 days

Subadult (2-3 yrs)
2 large fuzzy mice, small hopper mice, or pinkie rats
Every 4-5 days

Adult (3-6 yrs)
2 adult mice, or fuzzy rats
Every 4-5 days

Large Adult (6-10 yrs)
3 large adult mice, or 2 subadult rats
Every 5-7 days

Hope this helps you figure it out..

Hey VegasSnake, is that you Jason?