The plywood panels are only placed on the benchwork temporarily, as they will be removed and cut to allow for raised elevations for the city level. I also expect to lay down at least a 1" base of styrofoam on the bottom level. Maybe. I really don't love working with that if I don't have too. I may end up using risers for the roadbed and styrofoam surrounding it...we'll see. The concept with this layout is going to be very urban, so not sure I'm going to need a lot of 'terrain' that would have natural rises and such.
This is starting to get fun!