Do you have any pink or blue insulation foam panel available locally? I purchased 2 panels in 1" thick x 2'x 8' long pieces. Cut them into 2' x 4' pieces and you have the basis for 4' x 4', 4' x 6' or 4' x 8' gaming tables. Paint one side black and the other green and you can switch between urban or country battles. You can even mix them up.
Next you need two lengths of 1" aluminum siding corner trim to slide them into along each long board edge. You could also put velcro on the mating edges to help keep them together instead. You now have a modular board that can be configured to three sizes. Please remember to use craft paint or the foam will melt. My cost in Canada was about $50.00 in total.
If your plan seems to be working...something's wrong