Hubs has made a sleeping platform for our van with storage underneath. The frame is angle iron with plywood on top; much lighter than framing the entire thing from wood. IIRC, he used a carborundum metal cutting blade on a circular saw to cut things to length, and bolted pieces together.
This 80/20 extruded aluminum looks lighter and slicker that angle iron and to have many applications for those into fabricating stuff; there are all types of joiners.
Here's an instagram pic from someone who used it to fabricate framing for a van conversion: instagram.com/p/BuCzVqPHs_t/
80/20, Inc: "The Industrial Erector Set" sells the stuff and they have photos of many applications here: 80/20.net/gallery