Here's a plan I have for making a 4x8" trench table, suitable for playing two games side-by-side at my FLGS. I plan on using two sheets of 1" foam sandwiched together with liquid nails so the trenches will be easier to cut out.
One will have a hill in the middle, while the other will have a valley/depression. Pink line separates the two tables, trenches are black, the little circles represent muddy craters, red line is P1 deployment, and blue line is P2 deployment for scenarios.
Movable terrain for each table:
traverse for jacks to walk over - 3 per side
8" sections of barbed wire - 4 per side
4" sandbag walls - 3 per side
8" shelled-out forest - 3 per table
I'm looking for input as to any game play problems you might foresee. I'd also like to know your ideas for movable terrain, especially obstructions.