When I really want to push a point like that (you WILL eat f/t, you WILL eat rats), it usually involves some sneaky stuff like that? But mostly it involves out-waiting the snake. Basically, I wait until July or August, when they're really, really hungry, and then I simply won't feed them if they won't eat rats. (You WILL eat rats, because there are no mice in the house. No rat = no meal.)

This is hard with females, because I desperately want them to eat and gain weight before October. And sometimes going through this means they won't be ready to breed in the autumn if we go through the hassle of switching to rats, when they would have been borderline if I left them on a mouse diet.

... so now I have a 1300 gram het lavender female who finally eats f/t and gave me 5 good eggs. But she gives even live rats the evil eye and won't bite.