Me x3,
Maybe it's just me but lately I see the trend of people putting way to much thought into simple things and expect an answer-all solution to be posted, it's good to ask questions and share answers thats how ideas and information are spread but the truth is most of the answers to questions posted should be used as a guide or a base starting point for YOU to go off of and tweak and draw your own conclusions from thus building your own experience/knowledge. There are far too many variables to take into account for there to be a cookie cutter answer.
Personally, I eyeball my feeders because I don't have time to weigh each one and I am not conducting a controlled study where each snake at Xsize needs a feeder at Xweight and I have never had a snake shrink in size, some have grown slower then others but that's more along the lines of genetics.