Top of a Chicken Tractor?

[jennyf]

My neighbors have very graciously offered to tractor some of my meat birds in their yard. The birds' primary space is about 150 feet away at my house, but I'm figuring hey, I can spread out the group (and poop) a little and let alternating groups of the birds get some fresher grass and sun. They would only be in it for some daytime hours. So bottom line, lots of getting put in the tractor, getting removed from the tractor. Tractor is just 4x6. What would you suggest for a top? It needs to be flat--I built the bottom and sides yesterday, just hardware cloth over 2x4s. I was thinking hardware cloth for the middle of the top with a flip-up plywood panel on both ends. Any concerns with that? How big should flip ups be? They will also have a huddle box for shade and shelter in it. The plywood I have on hand is 3/4 inch or 1 inch. If anyone has pictures of an arrangement that has worked well for them, pics would be much appreciated. Trying to keep it small and simple b/c it's only going to be used a few months of the year and stored the rest. TIA--this site is awesome!