The floor is done. Dad added more fasteners to the frame and it feels really solid. I spent a day cutting styrofoam insulation and filling in the cracks with expanding foam. That stuff sure is sticky! After a few other options were brought home, we decided on sanded certified 3/4" plywood for the sub-floor. I put a couple coats of floor paint on it to help keep it nice and protected through the process. The blue foam stapled to the corners is there to keep the trailer from wearing holes in the nice tarp.