We use 1/2” on top of all plywood. Screw it down with dry wall screws, paint it brown. Screw track to it. Never had a problem, no vibration, no noise. 18 x 38 feet.layout space.
Be sure to cut it with a knife blade in the saw. Virtually no dust. I cut a small piece Saturday inside the train room and cleaned it up with a shop vac in seconds. Usually do outside but the rain was really coming down.
Feel free to e-mail me if any questions.