I use DC-fix on my H51w and I really like it. I'm not a fan of the "pure flood" beam. I like the bright but diffused center tapering off in brightness that you get with a frosted lens and reflector combination. Paolos: the best way to describe the beam on the F models is just like this... you get a bright but diffuse center, the corona around the hotspot blends gradually into the spill portion of the beam, and the spill seem to get darker on the edges, at least to my eyes, with the reflector/frosted-lens combo. I really like that beam profile. I currently EDC an SC50w+ that I've had for over a year now, and I use DC-fix on it as well. Even with just a regular Eneloop or an L91 in it, at 107 lumens and the DC fix on it, it's plenty of bright for EDC use. There's an old cemetery at the top of a hill near where I live, and I take my wife's poodle out for at night up that hill usually. There's lots of tree cover and my 50w+ is plenty bright in that situation; it will easily light up the fence and wall of the cemetery from across the street, a distance of a good 40' or so. Even on the sidewalk up there and back, where there are the standard sodium vapor streetlights we have here in the States, the 107 lumens is still enough to brightly light up a good 15' - 20' in front of me, with the DC-fix on the lens.
In short, an Fw on its two highest settings will still give you a pretty decent range for the beam.