I am thinking we may be over thinking the OPs direction. This may be a tinplate loosie-goosie-kinda-maybe....temporary...roll of grass mat casual layout.
If so, maybe just position 3 sheets of 4' X 8' Advantech on the table overhanging 18" on the side and1' on the ends, kick back snap some track together and have some fun\ on your new 8' X 12' train table surface.
Maybe fasten some splice cleats on the exposed bottom surface. Those sheets can overhang and be leaned on w/o sea sawing up the opposite end. Lots of inertia weight.
Temporary being the operative word.
That Advantech is great stuff. Very different, less expensive, non responsive to moisture and much better than any plywood for decking purposes.
