Well it had to be done, twelve XML LEDs in a fan cooled case 
LEDs are on a multi finned alu heatsink but with a copper mounting plate.
Air is drawn up from the underside. I had space for a splashguard but the stem keeps the crud away. Its been out on some really wet rides - no probs.
Battery pack is Li-ion 14V 10Ahr. 1 hour at full bore, 3 hrs @ 4000 Lm (which is perfect for most of the rides) and theres a 10 hour setting as well.
My old Lumi Halide
Ahem.
And there's enough hot air blasted out the back to keep the hands warm on a cold night. Fan is actually a 50mm miniature blower.
:( 
