Greg,
As mentioned, screwing the track to the plywood would be easiest. Be cautious of two things: First, the screws would transfer vibration to the plywood, so I would use at most two screws, one at each end. You could get away with using one screw in the middle of each track section as tubular track stays connected. Second, if you do screw the track down, don't over tighten the screw which would compress the foam.