I much prefer the reflector in the FF. I've played with the cut down NX05's, even made a custom center section that spaced the NX05 out .070" from the emitter. It does make for a nice round beam, but virtually no sidespill. A properly modified center section with a turned SO17 reflector is much nicer for me, after modifying the head the reflector is the perfect size for the FF, you don't lose any of the actual reflector surface. After playing with every imaginable combination of optics, I now run the 17mm reflector in both my FF's. You do need the old style skirted reflector for best results, and they seem to have about dried up. Moving out the NX05 is much easier, but I don't like it nearly as well. To each his own.....
Dan C