The airline crate's a good idea, although if he's flipping the wire I'm guessing he might flip the airline so you may have to secure it in some way. If you want to stay with the wire, if you can I'd set up a camera to see exactly what he's doing and how, maybe you can prevent it that way. I had to do something similiar with my RB, Sandy, when he kept getting out of our yard and I couldn't figure out how. I finally set up a camera to figure out how he was doing it so I knew how to fix it.