The general guideline is to feed prey slightly smaller than the thickest part of your snake. My buddy is about year and three quarters/ two years old and feeds on small rats... I would say look at the thickness of the mouse and just be sure that it is slightly smaller than the thickest part of your snake. Feeding one prey item rather than two is a good idea because digesting two mice is much harder on the digestive tract than digesting one. Glad to hear that your BP is a good feeder though