Reply to "Tabletop question: Foam on plywood"

I have 3/4" thick rigid foam insulation board from one of the big box stores glued to plywood. It was painted and turfed. I have kneeled, leaned and stood on it with no issues.

One advantage of using foam is that makes a nice and easy surface for mounting anything that has to "stick" into the layout, like trees, signs, crossing flashers, telephone poles, etc.