Box I did for 2 18's was around 5 1/4 cubes each as that's all he had room for and they slam....
Even tho there prob gone by now any idea on a the next shipment and that 7-8 cubes was that whats recommended for 1 sub? SNAP!!! I thought I might be able to squeeze a box in my eclipse hatch back. I think I got about 5 cubes back there.