The general rule of the thumb is to feed a prey item that is 1.5 times the size of your snakes midsection...If you feed him and pinky and there is no bulge, I would move up to two pinks per feeding...How often after eating is your snake pooping???If he is going within 2 days, I would suggest you move up to 2 pinks...If you follow this guideline as your snake grows, so will the prey items..
HTH,