1/2 flat wounds plus RBX375?

Tom "T Bone" Wolk did it on a Fender Precision but I believe he did a reverse of what you want to do. He used roundwounds on the E and A and flats on the D and G. If I'm wrong, I'm sure someone will correct me. To me, that was always the problems with flats, a dead E and an almost dead A. The only person who will know if it will work for you is you.

 

Nothing wrong with that as long as it sounds good. Co-Worker of mine has a similar setup. Sounds good to me (as well as for him) and no complaints so far. He uses flats for the E & A and nickel rounds for D & G. When he does pop and slap, the flats still slap well and the rounds pop as they should. For stuff like blues and rock, he tries to remain on the E & A and it keeps that nice low-mid end that flats give with the extra zing when he does fills on the D & G. Pretty cool and I don't really see a harm in giving it a whirl.

 

That kind of setup would drive me nuts. Go for it! :-D

 

Wasn't there a big name bass player who uses a flatwound B string on his 6 strings?

At least I heard that...