How big is your Heat Sink???
The enclosures are based around the heatsink. They tie into the sides, and then down to meet the splash shield.
As far as doing DIY on composites, go here:
http://www.fibreglast.com/category/Learning_Center
It has a ton of information that would cover making any composite part.
UPDATE: I re-worked the 22" fixtures to have 60 leds in each instead of 72. And I switched to just 12 whites, 36 RB, and a mixed string of Red, Green, UV, and regular Blue. I can now run the fixture closer to full power and easily get the 20K look. At full power, it seems brighter than the 400w 20K Ushios I had before. I still have them turned down to around 70% power to better adapt the corals.
I am making the buttons for the boostled.com controllers now. They will be clear plastic. I'll update with pics asap.
Mike