Custom built grow cabinet - need some tips

Just finished framing out my cab (4'3"W, 2'6"D, 6'H). I have a 400W Hydrofarm Digital Sunburst and the exhaust system isn't the greatest as you can see from the pics.

So I'm trying to think ahead of time how I can keep the light cool with this shitty cooling system. What type of fans do you guys think I should use for intake and exhaust? Also, what about light proofing the intake and outtake holes on the cab? I saw Rumple's DIY lightproof for PC fans but how would I do it with a bigger fan?

Thanks

A carbon filter will eliminate most light. You may want to buy darkroom vents for your intake so there is no light leaks

PVC elbows can light proof intake holes. I'm not sure about the exhaust. If you have flexible ducting you can bend or curve it. Light can't turn corners.