Proceeded with marking the hole locations for the AN screws for attaching the large floor to the support previously riveted to the small floor. Used rivet spacer to mark the hole locations, I wanted to match drill the holes to makes sure the floor goes together nicely since it will be getting removed and reinstalled periodically.
After marking the holes, removed, final drilled, deburred and dimpled as required. Riveted the nut plates to the new support, and test fitted the two floor pieces together.
Reinstalled the small floor and ran the CAT duct from the NACA vent, through the floor with grommet edging and through the aft baggage compartment and avionics bay to the eyeball vent location on the instrument panel.