So what does support the 13/16" thick floor boards? In a nutshell, floor joists. The joists are 2" thick by 1-3/4" wide. There's a stringer, fiberglassed into the hull, upon which the joists, running athwart, rest upon. The joists are fixed to the stringer by fiberglass. According to Tommy Chen, inside the stringer is a wood called 'Yako' which is very much like iron wood.
Looking forward and outboard on the starboard side. The stainless water tank is forward.
Looking outboard at the floor support structure. Starting at the bottom are: (1) turn of the bilge for the fiberglass hull; (2) a stringer fiberglassed to the hull; (3) a floor joist that has been fiberglassed to both the stringer and the hull; and (4) a fixed portion of the floor.