I have been carrying a prototype LunaSol 20 that sports a XP-G behind the original reflector. I say original because the reflector being used in the LunaSol 20's out there have been modified by a small removal of the rear of the original reflector (~.015" as I recall). The center reflector in the LunaSol 20 is the McR-12. I believe the McR-12 will work at its best with the XP-G if it is elevated slightly above the ceramic case of the XP-G. I mentioned a prototype LunaSol Elcipse elsewhere and that is what this particular light is. The XPG has three levels of output. I consider all three as having good utility by virtue of the flood type beam. The spot on low has merit because of its relatively large angle of coverage, IMHO.
I have been doing some bench testing of the XP-G for my own interest as well as in some joint interest with a couple other light builders. Although the package is tiny, the apparent image and source of light is not as small as one might think. I believe this had been addressed in other threads already.
I had some custom MCPCB's made to host the XP-G and function in my present Light Engine assemblies. I was very pleased to find that one of these light engines screwed in behind an original McR-20 reflector (Luxeon III based and pre-joker) in an Aleph 2 head with very acceptable results, IMHO. By my reckoning, the ideal focus was found by elevating the rear of the McR-20 ~.010" above the rear plane of the XP-G package or in other reference, .010" off the MCPCB itself.
Behind the McR-12, the XP-G will give you a large spot and the intensity of the spill is not radically off that of the spot. I personally don't care for high contrast between spill and spot but obviously this is not a candidate for great throw.
