DIY Hood questions

[BlazerFRS]

I'm planning on building a hood for the 10 [acronym:65c2e524e6="Gallon"]gal[/acronym:65c2e524e6] tank I'll be picking up soon. Basic design will be super simple; I'll probably remain reasonably close to these instructions on Cichlid forum: http://www.cichlid-forum.com/articles/diy_canopy2.php

I plan using a 2 x 13 Watt Bright kit from ahsupply, along with some simple reflectors made from some aluminum flashing I have laying around.

I'm assuming the basic bright kit is not waterproof (although it may be, anyone know?) so I've been looking for a clear plastic sheet to put between the fixtures and the tank (probably good policy, even if the bright kit is water proof). I looked in Chase Pitkin, and all they seem to have is Lucite; completely clear and indestructible, but $8 a sheet... a little steep for what i'll be using it for [acronym:65c2e524e6="In my opinion"]IMO[/acronym:65c2e524e6]. I believe [acronym:65c2e524e6="Home Depot"]HD[/acronym:65c2e524e6] carries the sort of clear plastic one usually sees over florescent fixtures in office buildings and public places for about $2 a sheet.
My concern is that the less then clear plastic will reduce the wattage that gets to my plants... has anyone used this stuff, or have any idea of it's performance?
Any other suggestions for a material that could fit the bill?

[acronym:65c2e524e6="Thanks in Advance"]TIA[/acronym:65c2e524e6]