Ok - results! I believe I got the focus as good as it was. It seems somewat harder to focus now because the beam pattern looks so different, but the center is still the emitter shaped hot spot. The best I could get it at with a fresh Powerizer again, was 240 kcd, so a drop of 24 kcd from the 264 kcd measured without the focus ring.
With the focus ring, really weird - you can see the star exactly as it is in the beam, including reading the "Noctigon" ("nogitcoN") lettering pretty clearly.
I was thinking of reversing the focus ring - small end at the emitter, bigger opening pointing out - kind of like adding a reflector boost to the aspheric effect. Whay do you think? Think that defeats the purpose though...