So I put some D'Addario flatwound Chromes 12s on my Fender Jaguar (loaded with Curtis Novak pickups, BKP don't make Jaguar pickups). What a revelation! No buzz, almost immediate tuning stability (always a problem on a Jaguar) and the brightness of the Jaguar pickups + the 1 meg pot are perfectly offset by the mellow nature of the strings. Plus the sustain problems of the Jag have gone as the thick strings carry the tone. The 24" scale also works perfectly with the 12s - and the rhythm circuit sounds like a Jazz guitar - great for chords
I had heard that Leo Fender designed the Jazzmaster/Jaguar with flatwounds in mind and having tried them, I think flatwounds do seem to bring out the best in the guitar.