Hmmm...that's a tough one. I've eaten frog's legs, and although I sous vide a lot I've never done them! I'd probably start out cooking them like bone-in chicken but probably with shorter times (probably not a big salmonella risk, but I'm not sure). That is to say, maybe 130 on the low end up to maybe 140. You'd probably just have to try a few at a time...unless someone here can offer a better answer.