I've just gotten some Deep Talkin Labella Flats for the 4001.
I've been using rounds, which accentuate the highs. But I've got rounds on my P and J basses, so I figure the Ric and my Hofner can do the flat wound thing.
I'm excited about getting them on. Also going to remove the horseshoe cover so I can more easily dampen the strings when I play.