If your cutting the letters out then back them with plexiglass painted with a clear enamal (red and blue). The existing lights should give you a wonderful 'glow' effect to the lettering.
thin plexi is fine...and yes use transpairnt enamel from the hobby shop. A thin coat to begin with and add more to get the effect you like best. actully 1/8 th inch plexi is fine...either glue in it place or use small screws. colored window tint would probubly work as well...
I was talking about attaching the plexi to the door. For the unevenness you might want to try some CROME egg crate...it IS after all light difuser and should even things up a bit if placed between the lights and the tank. closer to the lights without melting the better...
Yeah..put the plexi over the lettering cutouts. As far as the eggcrate goes, I've tried everthing but that. I had glass cut to fit the holes at the top of the tank.(center is 2' of 1/2" factory) All the lights are sitting on the glass. Is this bad?