I've completed this dual Luxeon V bike light, similar in design to the 3xLuxIII I finished a few weeks back.
Once again I used one inch square aluminum tubing to construct most of the light. 20mm IMS reflectors are used, although I experimented with optics also.
I used a Downboy 750mA to drive the LEDs and a DPDT switch with center off to allow, one on, both on, or both off. It is powered by a 14.4v, 2500 mAH NiMH battery pack. One issue is that when fully charged, the 14.4v pack is over 16v which causes the DB to overheat (starts to flicker and freak out) it's designed for a max of 16v. I will probably replace the DB with a 700mA 3021 Buckpuck which can handle up to 30v input. It also turns out that I really like the dimming capability gained using the Buckpuck by just adding a 5k pot, and the Lux Vs will be a little happier at or below 700mA. I think I will like this better than the one or both on approach.
The light warms up within a couple of minutes if it's just sitting in the house, but on a test ride at about 10mph in the cool night air, it remained icy cold. The thermal mgmt plan for this light does not intend for it to be run for long while sitting on a desk... it is intended for night time trail riding and I usually ride 2 nights per week in the winter months.
Here is a link to some more pics of the Dual Lux V and a few beamshots: http://myfwyc.org/Timberlake/DualLuxV
Link to the construction of my Tri LuxIII bike light: http://myfwyc.org/Timberlake/BikeLighting?page=1