Just put some 1/2 inch hardware on the inside, up about 12 - 18 inches from the ground to keep the fuzzybutts from slipping thru the openings and prevent reach thrus, plywood is excessive and blocks you from watching them. Also a skirt laid around the enclosure will stop diggers, doubt they can lift a panel but they will try to burrow under it. If you have climbing or flying predators in the area, you might look into a prefab kennel panel from Lowes or Home Depot (available in various sizes) as a top plus it's strong enough to support a tarp for shade.