I have pretty much the same size cab with 400w hps. Got one inline fan over 250cfm pulling air from the fresh air through the cool tube, then one pulling the air out of the cab and then holes in the bottom of the cab to bring fresh air. Temps inside is high 70 low 80 (air conditioner broken) inside cab is 85-88
Yea i know, gonna hopefully get a portable swamp cooler to put by it to pull that air. Yes, I think i wouldnt have an heat issue if i had a cooler room temp. Gonna drill few more holes for fresh air to pull.