Want feedback on material to use for 2" thick foamboard layout framework

 I resemble your maladies and empathize.

I have used 2x2 wood uprights, and "L" girders made from 1x2s and 1x3s. VERY light weight and strong. I wish I could remember the book I have (had ) about it. The entire book was about open grid layout tables or some such thing. I'll poke around, but am sure someone else will know it.

I recently needed a table to butcher a 300 lb. pig. I pulled out 4 2x2s and made 2 "L" girders as noted. One then adds  some lathing as cross supports and me and the pig had a great time. In fact I had some of him for breakfast today.

Lying rigid 2 inch foam on that should work. Consider how tall you want it for access.

Ernie

I use a 1x4 box girder construction with 2x2 uprights. Think a box 2x5 foot made out of 1x4 with 2 x 2 cross members every 10 inches. Weighs about 10 puounds without legs for each module. Of course it will weigh a little more with scenery and such. But not much 

I used 2" pink foam for a Halloween layout built back in 2009. To stiffen the foam, I used Liquid Nails foam glue to attach paperboard angle pieces salvaged from TV packing material. It has held up and performed well.