Here's another option. I've got a SFE and when I got him he could, if motivated, squeeze thru egg crate. So, what I did was stacked and offset two sheets of egg crate and used tie wraps to secure them. I then put bags with marbles in them on top of the egg crate for a few reasons (if something tried to escape, the weight will keep it down, I can't accidently slide it off exposing a hole, wind from fans can't move it, etc.)
Light still gets thru fine, heat isn't a problem and I get the evaporation I want and the SFE isn't getting out thru it.
Take your time and make sure you get the cuts done well. It's super easy, just get a pair of pliers and start snapping. Keep going back and measuring and test fitting.
HTH,
Chris