I can't remember anyone modding the Matrix 2. Still, I have a tender spot for my Matrix 2's.
Until the Zebralight came out, the Matrix 2 was the only headlamp that fit my personal criteria for going into my earthquake kit--LED, water-resistant, uses as few AA as possible, no separate battery unit.
I have two of them. They're rather dim and greenish by flashaholic standards, although in truly dark conditions, they do fine. And whenever I actually have to do something with my hands, I always grab a Matrix 2 to light the way.
I had seriously given some thought to buying one of those PR-2 EverLED units that Arcmania had modded with an SSC P4 a while back to turbocharge my Matrix 2's, but at $50-55 IIRC, that was a bit rich for my blood at the time. I sort of regret not buying one, though.