Reply to "Tabletop question: Foam on plywood"

I am using 4" foam on top of plywood, reason I did it was for some of the sub track level effects I want to do (or may do). I am still early with it so can't talk about the noise level, in terms of holding down the track if ballasting that will hold it. Screws should work, putting caulk or glue on the screw tip should work as long as the screw is smaller than the hole in the tie (if you screw the screw through the tie, the glue will be rubbed off). I plan on ballasting my track and using that to hold it down, have debated using cork roadbed under the track, not sure about the cost of that vs rewards yet (fortunately my track is not laid down yet, makes it easier if I decide to go with the cork roadbed.