Cool project. I work with lighting, so I had some thoughts that might be helpful.
I'm sure you know heat kills LEDs. Typically LEDs are rated at 100,000 hours, but as soon as manufacturers cluster them together, the rated life drops down to 50,000 (for the honest manufacturers) due to heat. It looks to me like you are going to have a very high density of LEDs with out a particularly thermally conductive surface to dissapate the heat. Are you using fans for cooling? Maybe this is not such a big deal, but if you are going through all the trouble, you might as well keep them cool and extend the life and light output.
Anyway, I know acrylic is an OK thermal insulator so therefore a bad LED mounting surface, while aluminum is a good thermal conductor and is why most commercial products are mounted to an aluminum housing. (I know Sylvania's new tri-color LEDS are mounted to a sticker which then gets "stuck" onto a heat sink)
These are a couple of top notch products that I've used. It may be possible to look at their cutsheets for clues as to how they are mounting/disspating heat as you never use fans on commercial products (too unreliable, plus they don't work too well outdoors).
Check out the IO Line 2.0. The unit is basically one very solid aluminum extrusion that acts as the heat sink. These are 1-watt LEDs.
http://www.iolighting.com/
Also, check out the Altman Spectra series PAR64 LED fixture. We are using these to light a color changing tower. Also impressive light output. I think they are clustering 36 1-Watt LEDs in something about 12" in diameter. That is a lot of heat.
http://www.altmanlighting.com/
HTH
Mark