I have many medium length (<3') extrusions from 80/20. It was used for so many areas of the factory where I worked for machine guards and secondary operation fixtures. I also have some metric pieces from another manufacturer. I didn't take company stock, but rather from the scrap bin. I was amazed at what they were throwing in the scrap bins, such as aluminum extrusion, stainless steel plate & shafts, and some c/r steel. Usually the hardware was high quality stainless, not the hardware store stuff.
Anyway, I've used it and built with it many times. I have a few longer pieces. When I suspected one of my Harley frames was out of shape, I made a motorcycle frame alignment & squareness checker, with a long 4x4 section for the backbone. It was super rigid and showed the frame to be way worse than expected. I'm eventually going to resize it to use it under my Logan 200 lathe since I need a custom height stand (I'm in a wheelchair).
I've seen large boat trailers built with similar aluminum extrusion, so it's very capable stuff. I believe I'm going to rebuild my motorcycle trailer with it, too.