I bought a used 5 string fretted here but ordered by mistake an extra set of La Bella Deep Talking White Gold flats so I was able to try them on my fretless. They are thicker but are flexible and I think lowish on the tension but not as slinky as TI jazz flats which I actually don't dig ). The G is .63 and I love it because it's like putting guts on the D and G of my upright. The white-gold's (really brass) are brighter, even brighter than the Ernie Ball Cobalt flats. So yeah I strung my fretless with these strings and love them, clear but no finger noise and a I have a nice growl or low purr. And if you are into harmonics, you can coach a lot from these unlike regular flat. / It was perfect for my 5 string fretted which I strung E-C for a project I am doing with an acoustic trio
This guy Andres Rotmistrovsky ( I am positive he is originally from Argentina ) - uses La Bella DTF whites and blacks. Check these out for direct to preamp sound.