good rule is intake is always at the bottom and outtake from the top heat rises quickly you want that heat out first.

i use a small box myself 32x16x16 and can squeeze 2 plants in there growing using the LST method otherwise the plants would quickly outgrow my space.

i have a single intake and outtake and my temps stay about 80-85 a little warmer than most people like but not a problem for me they grow insanely fast once past that 2 week stage.

for you id make 2 hole up the very top on opposite sides same with the bottom that way air travels through the entire cab