Making kangaroo transport bags

We need to make big strong catch-up bags for kangaroos and wallabies. We hope we'll never need them, but we must have them in case we do. If we have to transport kangaroos in an emergency, we "pouch" them as if they were joeys. For a 20kg to 40kg kangaroo, they need big very strong bags - and they have to be easy to breathe through. So there is an art to designing and making them.