The best part about these is there are no welds. the whole thing is bolted togeather. To alay any concerns about that, I use a heavier grade version of the extruded aluminum to build machine tools and customized automation equipment frames. As long as the bolts are the torqued correctly they are not coming loose. This bolted extrusion is what lends itself so well to attaching extra stuff the the traielr frame without having to drill holes in it.
These are the primary reasons we chose to go with alloy for our Tilt trailer build. Welding alloy will ruin the tempering and create a lose of strength ~50% in the heated region. Welds typically fail before the section does, the opposite of a steel weld.
We also went with a Torflex suspension axle...no springs to rust out!
Been running it for 2 years now...done 2 trips to Houston & back (~3000 miles each trip).
Here's a webpage with more details on the design:
Tornado Tilt Trailer Build 
