lol This happened while I was writing my other comment but I couldn't resist replying.
Ha... As someone who keeps garters, which are known for their frequent bowel movements and messiness, I can honestly say I've never once had an issue with constipation from f/t mice. It takes about a day maybe two tops for it to completely go through their systems.
I wish you luck with your temperament experiment, but I'm honestly in doubt as to whether snakes have the proper mental hardwiring for true 'domestication'. Usually domestication involves a component of social dependence on humans for food or shelter, and I just don't know if I think snakes
have the capability to truly connect those things with us. I think you could definitely breed for bolder/shyer/calmer/whatever snakes, but I'm not sure if it would really qualify as domestication in the true sense of it since they can't really be 'social' with humans. (Not saying they can't interact, but I don't believe they have the capability to think of things that aren't in their immediate environment; like I honestly believe I cease to exist to my snakes once I leave the room)