Nope. I have been able to change all my snakes over no problem. Boas are not picky and will usually eat anything hung in front of their faces.
The only snake i havent switched from mice to rats yet is Luna my dumerils but she is still small enough that a mouse or 2 work for her. I'll work on her after she clearly outgrows mice. All the baby boas instantly grabbed weaned rats when i showed them, no hesitation on it being new prey or anything. They just said 'FOOD!!" and wrapped it lol.
And yeah, i heard a couple people call little baby mice and rats "jellybeans of fat'. Also just heard a guy call GTPs 'Ball Pythons on a stick" lol. Kind of true though. Pat is like a bump on a log all day long. I only see him move if i bug him or he moves from the cool side of the perch to the warm side under his CHE. He gets pretty worked up when he smells food also. Come night though, he is far from a BP. The little booger is on the move all night long unless he just ate lol.