Hi Joe, Looks similar to what I built, but I'm trying to understand what you're doing with the glass under the light. Why don't you get a sealed reflector instead and duct it for cooling? Unless you're trying to watch your $$.. I use a 600w digital with HPS and MH conversion bulbs, air cooled reflector. I'd also watch your dimensions, my box has about 18" in the bottom chamber and it's not quite tall enough, I'd recommend 24". The overall dimensions of my box are 48" W x 28" D x 86" H.

Here's what I built: Who says bud and power tools don't mix!?! - Cannabis Photo Gallery

and how it's doing on the first grow: First Grow, Bag Seed in Cabinet - Cannabis Photo Gallery

Good Luck!!

Farmer Rich