All enclosures, tubes and so on have arrived pre-cut for assembly. I'm now looking around for something to mount them on. It will probably wind up being water-sealed sheet wood, with a layer of paving tile underneath as ballast.
Just letting you know I'm still working on this. I had no idea a 4x larger habitat would be so much more work. Although really, moving cross country mid-project hasn't helped. Keep your eyes on this space, progress should be more rapid going forward.