I think it's been quite a while since I've posted to this thread, probably not since before I switched from halogen to LEDs early last year.
The latest setup is pretty simple, with a P60 flashlight drop-in module mounted in an old TurboCat light head and held in by a lens cut from an old Petzl headlamp. The module fits PERFECTLY inside the light head when I screw down the cap, giving good thermal transfer.
Needs it too, because the module is an XM-L (from nailbender on candlepowerforums.com -- VERY high quality work) driven at 2.8A. Supposedly around 1000 lumens from the emitter, and probably 650-700 genuine OTF lumens. I got a 3-mode module, which has 5%, 40% and 100% settings. Even the 5% setting it puts out more light than a lot of the old-tech bike lights and flashlights. On 40% I find it enough for most night riding as long as it's dry out, and 100% is
just enough for riding in the rain with my middle-aged eyes.
Batteries are 4 sub-C 4200mAh NiMH cells, recycled from the 14.4V pack I had batteryspace build me a few years ago, and mounted in a kids' water bottle. Good for about 100 minutes on high, 4 hours or so on medium and a whole lot of hours on low. Pushbutton switch is also from batteryspace, and the Andersen PowerPole connectors were prewired ones I bought off eBay. All told I probably have about $100 worth of parts in this thing.
Heatshrink and electrical tape on the connections look pretty ratty, but it's functional. I've also attached a shroud to provide a sharp top cutoff to the beam and avoid blinding everyone else. XM-Ls cast a pretty broad beam -- not as ridiculous as the MagicShine, but there's a lot of wasted light. The shroud is cut out of a yellow water bottle, and reflects enough light back down onto the bike to make it glow yellow. Wasn't intentional, but I think it helps conspicuity quite a bit. At first the glowing yellow shroud was hurting my own night vision, and one day at work I found a tea bag wrapper and taped it on so it doesn't catch my eye quite so much.
Because of the broad beam, I'm going to retire this unit to mountain-bike duty for which it's much better suited. My commuter bike is about to get upgraded to a dynohub, and I'll be doing a DIY project with that soon. Pics when it's done, or sometime thereafter.