im not judging, but ive noticed while watching my snakes eat that the rodent always ends up thinner once its in the snake from being compressed, a rat thats a 1/2'' or so wider in diameter than my bp never shows hardly at all. plus everyone has different thoughts on feeding, most of the info out there is just "general guidelines" that dont necessarily need to be followed to a "T", just my opinion
after reading your edit, ive heard 10% of the snakes weight is reccomended