Prey Size When Very Thin?

i had the same problem, i was feeding my bp too small prey items bc petco said that it would be just fine.... but my bp was thin, so i also read here that they should eat adult mice. i started feeding it adult mice and the first time it ate it, it seemed too big.. my bp put her head on the branch and almost looked as if it was using it to push down the mouse lol... the next week i fed a hopper, and it went down super fast.... so then the next week i bumped back upto an adult, and it went down quicker lol, and ever since then its been fast, and my bp has been getting fatter and fatter, and now shes all gravy =p