I had a 48"x18"x18" storage box when I bought my bus. I filled it with outdoor stuff (hammocks, chairs, toys, etc.) I added a 24"x18"x18" battery box and two 36"x18"x18" boxes for tools, extra fluids, hoses, cables, etc. More boxes would be nice - I'd add firewood, more outdoor equipment, etc. Laundry would be way down my list. Unfortunately, it would require some cleverness and probably some extensive fabrication to successfully mount any more boxes than I have now.
Buyers Products Black Steel Underbody Truck Box w/ T-Handle Latch (18x18x24 Inch) https://www.amazon.com/dp/B005S5BF6U..._oYXuDb35WXP6N