I use roto77s on my 4 string and have a 5 string jazz with rounds. Really not into brightness and twanginess at all so i'm toying with the idea of sticking some flats on that too. But i'm wondering what that B string is going to sound like - how much definition/clarity do you get with it? What have people found are the best flats for that low end to maintain clear notes? Is it worth just buying a set of four and keeping the B as a roundwound even? Or is it even an issue? I know i know.. only one way to really find out, and that's try them. Just interested in peoples' viewpoints on it. I know the rotos aren't the darkest of flats btw, and i'll get round to trying some others soon... the thing is they just look too cool on my badly painted bass which has a black overcoat and red undercoat showing through.