I love those custom-made enclosures. Awesome!
We use the basic kittywalk on our raised deck in the summer. I have two walks that are each 6 feet long. I can couple them together and make it 12 feet. It took awhile to get the cats used to them. Some cats want nothing to do with them, others like them, others try to chew their way out. They are easy to put together and dismantle. The metal rods that hold the framework together are corroding where they join each other. We get a fair amount of rain and humidity here. I would give them a thumbs up, if caution is used.
Caution: I never leave my kitties unsupervised in them. A dog, stray cat, wild animal, or bird of prey could attack the cats even in the kitty walk since they are collapsible. I've never put them on grass since my yard is not enclosed and not predator proof.
