Body fiberglassing for strength

The body will not be permanently attached to the floor so it will lack the inherent strength a floor would bring. With that being said, I need to take the flex out of this paper thin shell. Looking back at other threads, 2.old.2.fast suggested to someone that using the green Styrofoam that florists use to line the interior and then fiberglassing over would provide plenty of stiffness. The interior will be spartan except for the bucket seats. Probably some kind of interior just to cover up the fiberglass work. What have you guys seen or done?
Here is the tub setting on a wheeled platform ready for some love.


Here are the seats. The aluminum floor will be covered with XMat and some kind of carpet.

 

2.old is right. It needs to be a polyester based foam like this foil covered insulation I get from Home Depot. It's a dense foam that's the same thing as
gap filling expansion foam and comes in 1" and 2" thickness. You just peel off the foil. Cut into strips, carve it or whatever you need. A good polyester construction adhesive will hold it down. Then glass over it for a double wall.

 

So, your floor and firewall are attached to the frame before the body is attached? Interesting, and gives me something to consider.

 

Here's a general guide for how much MEKP to use under different outside or shop temperatures.