Plywood side thickness?

I am starting a 4' x 10' modernaire. I need to save time and weight. I would love to do a sandwich wall but want to get the thing built.
If using a quality grade ply, will 1/2" be good? 5/8"? 3/4"? It will be used as a utility trailer hauling tools more than camping.
Thanks,
Peter
If using a quality grade ply, will 1/2" be good? 5/8"? 3/4"? It will be used as a utility trailer hauling tools more than camping.
Thanks,
Peter