The floor is 5/8 in. AC grade Brazilian plywood of unknown species. I chose it for its thick veneer and relative absence of voids. Four 4 x 8 ft. sheets are laid transversely over the factory vinyl/felt mat. They are joined with 3 x .125 in. bands of 6061 T-6 and countersunk 10-32 machine screws into T-nuts. The floor is hardened and given some degree of moisture resistance by 3 coats of acrylic sealer/varnish.
Flanged L-track predrilled on 4 in. centers is mounted at the belt line with 1/4 in. flat head screws, hardened washers, and stop-nuts. Only a few blind locations near the C-pillar require riv-nuts. The aft-most mounting hole encroaches slightly on the boron-steel pillar and required the use of a carbide drill.
The lower factory polypropylene panels are replaced by 1/2 in. plywood wi<big><tt>th 1-1/2 x 3/4 in. (actual) poplar horizontal rub strips. The lower strip is centered 6 in. off the floor to work with cases and dollies on 4 in. casters.
The cavities behind the plywood are stuffed, to the extend possible, with R-19 glass wool.
A Tuffy Products storage box is located above the right-side wheel well to provide lockable storage for small objects while consuming minimal floor space. It encroaches into the floor about 2-1/2 in.
Going forward I intend to insulate the remainder of the walls and ceiling, reinstall the factory polypropylene panels, and add a ceiling liner (most likely Coroplast on all-thread standoffs).
I'm adding 12 volt electrical outlets at several locations (up high to avoid damage) and a 3 position switch for the cargo lights (always on, always off, Ford auto) by the right rear door.