discreet

Done that one many times so, I used rounds and didn't change them for years. In the end they sort of sounded like flats but still played like rounds. Did a very good Clash sound. Bonus! I've just changed them after 5 years or so as they didn't record (straight into the desk) very well. Another BC'er has them now as he wanted some dead rounds. You never know, in 5 years you could have "that" sound too! 

Back in the day I used Roto 66 Swing Bass and preferred them after they'd lost their twang. Then I used DR Fat Beams, and preferred them after they'd lost their twang. Then I discovered La Bella flats and loved them, especially for recording. Now I'm using Fender 7250M nickel-plated steel and love them. I'm yet to discover if I prefer them after they lose their twang - because they haven't lost their twang yet. They also have the advantage of being £13 a set. I'll still use La Bellas for recording though (mainly), you can't beat La Bellas played with a pick à la Joe Osborn...