Don't worry and keep giving them what they want for now. As long as they are eating is the bigger thing. You can always try to give something different at another time or when a different feeding time is due. These snakes are captives and the least we can do is feed them what they like to eat. When they want a rat you will be the first to know. I used to sweat over it and then a light bulb went off and I stopped forcing the issue. Good luck and relax as long as he is taking in food!You can start by trying him with a jumbo mouse in the next couple of weeks and see how that goes first.