I tried a Luxeon MZ (90CRI, 5700K)in a (desert tan) Convoy C8 today. The build was straightforward, I used the stock XP-type board and a Convoy OP reflector. Just the centerpiece was a bit of a challenge: because the led is slightly rectangular and should be off-center a bit, a simple round hole does not work. I made some cutouts in a butterfly-type XM centerpiece, that worked. A bit off-center would perhaps even help getting rid of a donut hole.
The result is not what I hoped for. The output is good, over 1400 lumen and I can get more out of the led if I use a better cell (used a PF for a start). But the beam has a too pronounced donut hole despite the OP reflector. Much more diffusing is needed than that. On top of that the tint is not as good as maukka’s tests made me expect. The bare led at 0 degrees measures 91.3 CRI with a R9 of 69, tint on top of the BBL (maukka measured 95 CRI and R9=89), and the hotspot measured just 88 CRI with R9=46 (changing the AR-coated lens to uncoated did not changed that significantly).
The result now is that I do not feel like finding the ideal diffusing method (changing focus of the led and/or frosting the lens) for this light, but just think of a next nice led to put in that has not a quad die.