I dont quite understand what kind of light fixture youre building but I use flouresvent bulbs in clamp on style light fixtures. I have two that I use mounted on PVC pipe which stands in the center of my 16' boat from the center console, one pointing to the front of the boat and the other pointing towards the back. Amazingly, I'm using "13 watt" bulbs and they do great. I believe their lighting is in comparison to 100 watt regular bulbs and they are hardly any drain at all to batteries. I thought I was nuts paying this much for bulbs but so far, so good. If they'll last me a couple years I'll buy again. They light up the boat very well, all my rod tips, and throw a light pretty good out the boat as well (better than standard bulbs). They are soft to the eyes, and never get hot. Here's the link I ordered from since I couldnt d any local.
http://www.solarseasy.com/cfbulbs.html