I guess the worst I have glassed have had 8X10 holes in the front floor. I simply pull the carpet out of the way and lay a glass mat over the entire front bucket and up on the tranny hump 4 inches or so. Then I cut 3 or 4 more mats to fit and then I mix the resin. When mixed I quickly paint the floor and lay on the first mat and then paint it and then lay the next mat on and paint it and so on till done.
After the thing is hard and the carpet is resting on it there is no difference in feel by your feet. And it lasts as long as a metal floor. (longer)
The last one I did is on the Wrangler my son drives every day. (He bought an ebay Jeep from New Jersey) The rest of the floor is passable and only the passanger side floor was in such shape.
Big JIm