Can’t seem to find these....

[fishhead0103666]

Yes, I don't want to have to worry about the wood warping or falling apart when it gets wet over the years.

 

[TheWolfman]

4x8 is standard sizing for plywood. I’ve never heard of anything wider then 4’ maybe longer like 4x10 but never wider. I would suggest using two sheets and split the difference, so two sheets cut to 2’6”x8’ and butt up the factory edges.

 

[TexasMFK31]

5x10 sheets exist I know. The lumber mill here that I get my wood from has them. But, I live in Houston Texas where I can readily get most things. Hopefully you could find one semi-locally.