03-14-2012, 08:30 AM
I would second Andrew's comment that a layout sits on more than the roadbed and subroadbed. I did an N scale layout on 3/8 inch plywood, and I suppose that's acceptable for N, but you do have other questions -- is the layout sitting on shelf brackets, open grid, L-girder, the tops of bookcases, or what? And while it's popular these days, foam is very noisy and can certainly detract from the effect of sound-equpped locos. It probably depends on where you are in your progress in the hobby, what your expectations and priorities are, and so forth, so there simply isn't a single good answer to the question!