Suggestions to rebuild floor hatch over gas tank 24 offshore

[ScottyCee]

Adding a couple of pics from my take on this. I liked the foam, and now they are easily handled by one person. Before - not so much! The supports are 4 layers of foam with glass cloth between them and then wrapped in a final layer. Very stiff floor now for almost no added weight...

 

[Sparkdog118]

I looked into coosa board and it is basically what you fabricated with the fiberglass layers. They say it is made for transoms and is Good but overkill for hatches. 1 layer of 1/2in divinicyl made my hatch rock solid.