I switched out the wood blade in the chop box to a metal blade. Makes a pretty good cut-off saw.
My welds aren't the prettiest but their strong! I welded a 2 foot extension to the back of the trailer and 6 "outriggers" to the sides. I also plan on drilling and adding a couple bolts on each side of the rear extensions.
Side view. Built the first of three platform/foundation sections. My first time working with metal studs and I can tell you that they're great! I cut them in groups on the cut-off saw, screwing them in place is fast work, and, if you make a mistake and need to adjust, its as simple as re-screwing.
I used old bed rails for the side angle iron. It's "spring iron" so, to my surprise, it welds great. Just really difficult to drill threw. There's about a 1/2" gap on each side so that when the siding is in place, it will sit down onto the angle iron. When the siding goes up, I'll screw the foundation to the trailer at the bed rails, and under the trailer.
And from the back.