IMO.. floors arent very useful in bench type boats. They dont add much advantage because you are still jumping hurdles and have to elevate every seat someone has to sit on(short pedistal), and the floor just adds a bunch of weight and performance issues become a problem unless your are running max hp.
I have modified several bench boats. What I do is run a deck from the tip to about 2′ behind the 1st bench(room for more storage or livewell behind front bench). Add another deck/enclosure in the rear going from the rear bench to the transom makes a nice area for driver to set stuff). The REMOVE the center bench and install a flat floor in the center of the boat. Aluminum *I beam* type supports under the floor work great. 3/4″ is fine for thickness. After I have the floor installed I run a livewell along the side of the boat(can be storage also) too add more functionality, and it adds structural support. The framing must be attatched to the floor and side of the boat. When all that is done, install a pedistal of choice on the front deck, a removable seat in the center, and a swivel seat in the back for yourself. Go fishing and kick your feet up.
Keep in mind this does add a lot of weight to the boat. If its a wide boat there will be less loss in performance, a narrow boat will sink in further and require more hp to get on plane. Its a good trade off.. speed for a comfortable boat.