Sill seam, vapor barrier, and finally, plywood floor!

The following steps happened pretty quickly, and the wind was increasing steadily, so photos are a bit sparse.
After cleaning up the scraps of cured spray foam from the previous steps, and ensuring no insulation (or foam) was higher then the metal framing of the trailer, I applied sill seam (a flat, spongelike polyethylene material) to all the metal framing.

This will act as a thermal barrier to reduce the transfer of cold temperatures from the metal framing to the plywood subfloor. I just taped it down every few feet since the plywood, once installed, will hold it firmly in place.
Then came the plastic vapor barrier, as added insurance against moisture intrusion from below, with some 2x4's to keep it from blowing away until the plywood subfloors go down.

The 3/4" plywood sheets had already been cut to length, notched for the threaded hold-down rods and fenders,

and test fitted prior to the installation of the sill seam and vapor barrier, since the plywood is heavy and rough, and would have torn these softer materials. So suddenly, and somewhat anticlimactically, the plywood floors are finally, and gently, lowered into place (thanks Marsha!) and it looks like a trailer ready for a house!

I used #14 (which are 1/4" diameter) self tapping screws, 1 3/4" long, to fasten the plywood floor to the steel framing.

I was skeptical that they would pierce the nearly 1/4" thick steel framing without my first drilling a pilot hole, but lo and behold, they worked like a charm. They have a drill bit point at the tip which makes a pilot hole, and two wings to clear the metal shavings from the hole (which break off once used), and then they proceed to cut threads in the steel and screw themselves in. A real time saver!

Now I'm ready to cut the 2x4 sills and start laying out the stud locations.