This is a mockup (model) of a one-wheeled trailer I designed using only flat stock, even the swingarm. It is a model of the frame only. That's a 10" or 12" inch scooter wheel and tire, and a suspension bicycle shock (no damping!).
I imagine using 1/2" or so aluminum and having it cut and welded at a local shop. The model is to show the shop guys. The main rails (the longest pieces) could be aluminum bar stock, or tubing, or something extruded. That might make them lighter.
The hitch is incomplete. You can see that I intended to have two draw bars coming off the plate that gets attached to the bike axle, at about 45 degrees. Instead, I plan a single hitch "loop" like the one in the drawing I posted.
You can also see that the height of the front assembly of the trailer is tall to match the original hitch design. It too will be lower profile like the drawing.
My goal is to have a rock-solid 100% reliable frame with a DOT wheel and tire that weighs less than 45 pounds. Some of the "utility" style two-wheel trailers people are pulling with their bikes are scary! Like, 125-175 pounds empty! Screw that! Even more, for campers and shit.
After the frame is complete, tested, tweaked, and re-tested, I have some designs in my head for a modular storage/hauling system to build and mount on the basic frame.
I want mine to pull and handle like the TrailTail. If you've seen the video on their website, you know that trailer can take some serious abuse without upsetting the dynamics of the bike. I think if they can do it with a <400 pound single pulling it off-road, then a 500+ pound Strom should pull 80-100 pounds (loaded) on the street like it's not even there.