Foam

Rather than paying $5 or $6 per 1 ft x 2 ft sheet of styrofoam, I decided to experiment with landscaping with extruded polystyrene, which comes as 4 ft x 8 ft sheets for about $12 per sheet at The Home Depot. I had to cut the sheet in half with my pocket knife to get it to fit into my van. I don't know how this works compared with styrofoam. For instance, how does paint or Woodland Scenics "Earth Colors" adhere? Since I'll probably use a lot of Foam Putty for landscaping, it may not matter.

I laid one of the halves down on the floor with the cutting mat underneath to protect the carpet. Then I measured and cut pieces: One 17.25 x 24 inch piece for the floor (slightly smaller than the dimensions of the suitcase so that it fit between the wedges at the "north" and "south" sides of the suitcase) For the mountains, I cut six 3.5 x 18.25 inch pieces for the "east" and "west" ends, six 2.5 x 18.5 inch pieces for the "north" and "south" sides, and twelve 2.5 inch
half-squares for the corners.

I want a trestle across the north side, but I cut the foam in solid strips and will cut out what is not needed when I assemble the trestle. The lower track fits snuggly into the opening, but will have more room when I landscape the mountain sides.