I'm very glad this thread is around, because my problem is that I currently have the Rotosound flatwounds on my fretless j-bass, and they sound great, BUT my bass' trussrod is at maximum possible tension now and I would like the neck to be a bit straighter. This thread helped me decide to try some of the lower-tension brands mentioned, which, if I've understood string tension correctly, should give me a little more room for adjustment.