Just feed it one or two of whatever it can just manage to get down it's head to put a very nice, noticeable, substantial bulge in it's mid-section about every 5 days when it is small like that and growing.
When a snake's gut has been used to only processing very small meals for long extended periods, feeding boat-loads of food all of the sudden can often lead to regurgitation issues, especially if it cannot seek the proper heat source temperatures to digest it. Snakes that eat very meger meals for prolonged amounts of time, and are somewhat thin should be staged a bit in their larger meal sizes.
Meals are too small when they can be easily gobbled down. When they have to work at it real well to get a meal down, and it stretches out their head and the skin on the body as it goes down and puts a very decent bulge in it's mid-section, then you know it is substantial enough..........simple as that!. Pinks and fuzzies can't even be seen in the mid-section of that snake, but certain sized hoppers/weanlings certainly would. Some fuzzies and hoppers are absolutely HUGE, and some are very tiny. You have to gauge it by the size of the rodent, not necessarily what is marked on the bag or pet store cage.
I know it is hard to believe, but there are some snakes on this planet that aren't Eastern getula, or floridana, so don't try to stuff your little Sinaloan like a Thanksgiving turkey as some would recommend. 
~Doug
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"a snake in the grass is a GOOD thing" 
