If you want stiffness, then you really need to use carbon rather then Aramid, IMO. I made by floors out of 5mm closed cell foam with 2 layers of CF on each side. They are around 450-500mm wide and very rigid. However my floors do not contribute much to the car's structural integrity (they were originally fibreglass anyway and the seats are secured to steel bars that are welded to the roll cage) which may be an issue with your car as the floors on steel cars often form an important part of the structure. Mind you, if your Avatar is anything to go by, you already know that :-)

What safety concerns do you have that require an Aramid floor instead of CF? Certain parts of an F1 car's bodywork (wings for example) have an outer layer of Aramid in order to keep the CF in one piece in the event of a crash. It is also used to reduce the risk of sharp objects penetrating the cockpit area.

With regard to bonding the floors to the original shell in order to retain stiffness, not easy IMO. Unless you have access to the high tech glues used by car manufacturers or race teams and a very stiff shell, you may have problems due to the different structural characteristics of the joined materials. My car is fully caged but, as said earlier, I am not expecting the floors to add much to the structure's stiffness.

If you plan to just remove the flat areas and are leaving the box sections in place, then a lot of what I have said is relevant :-)

Easycomposites recommended that I use their VuDuGlu VM100 for gluing my floors to the central steel box section backbone. If I was doing this on your car, I would seriously consider the belt and braces approach - glue (with a wide jointing surface) and bolt.

I am probably scaremongering here and others may well disagree with me, but I am guessing that the car will be abused? :-)

Geez, I can ramble on sometimes :-)

Steve