We always started out training our dogs in a blocked off room with linoleum for easy clean up and once they no longer made any messes at night we let them have access to every room of the house. We live in our RV now, so I realize it would be more difficult, but I believe if you are going to spend much time in the RV, you should work on house training rather than crate training so that you won't need the crate. We have had 3 dogs (2 older passed away now) travel with us and we never had a problem leaving them alone. They did not destroy things, or make messes. If the purpose is for potty training and no messes at night or when away, how about puppy pads for training until you can trust it.. And - I would never transport my pet in the trailer/5th wheel. They would be in the tow vehicle with me.