PSU I'm using is 7" long and the case supports just under 7.5" with the slot in front of it taking up by a fan or drive cage like how I have it planned. It didn't say whether or not the half inch difference was with the fan/hdd cage furthest away or closest since the bottom fan mounts are slots.
Another setup would be to leave 5.25" bays in, use the lower 2 front fan intakes, 3x HDD nearest front, bottom intake fan then psu at the back if that makes sense. I dont know what software people use to draw up a fan setup overlay on top of a case with the drive cages / optical bays removed etc but that would help explaining things.