Which flats did you try and what gauge?
I've tried standard-gauge Rotosounds and GHS, and heavy-gauge Chromes. I've currently got TI flats on my Warwick Flashback, and so far I'm not really impressed.
The Rotosounds sounded like roundwounds at first; after they "died" they sounded OK, but the tension was so high that my poor P-bass folding up like a pretzel, so I ditched them. The Chromes were the most comfortable, but had the worst "toy-like" sound, it was just too weak. The GHS flats were good and sounded similar to Ben Kenney from Incubus (whose tone I also dig), but still didn't get me where I wanted.
With the TI flats, they're a lighter gauge, but they're almost too flabby and flexible. I may try a heavier gauge later on.
