Need help designing flower/veg box 2x4x4

Hey guys im new to this site and have been reading on it for about a year now but finally decided to become a memeber. I have been also growing for a year now and have had pretty good yields with CFLs but its time i step up and get an hps for the flowering room. I want to design a dual chamber grow box with the dimensions 2x4x4. The only thing is i am not to good with setting up the proper air flow. So pretty much if anyone has a design i can go off of thatd be great or just throw me some ideas and what materials i need. I have a 2x2x4 grow box right now not really that well set up but it seems to be doing the job but its not light tight so i feel if i were to grow something besides autoflowers then id be in trouble with the light cycles and dark periods. So please post away and give me some ideas!!!

2x4s with 1/2" foam panels from lowes. I painted the inside with roof-gard 700. It's an elastomeric coating that's very reflective and water/ air/ light proof (for the cracks between panels)

If you don't have a vented hood or an ac, the heat will kill anything big enough to die.