We travel with our cat in our 17sd. We have a screen room on ours and the litter box under the bed. In the truck, its on the floor behind the front seat. The food dish is by the door under the closet door. The cat is always on a leash except at night. The cat's favorite place in the side table looking out the window. We cover the table with a towel. We store the spare litter in the truck and food under the sink.
When driving the cat is also on a leash in the truck and is NEVER allowed on the driver side and it only enters from the passenger side of the truck. He usually just curls up on the center console between us. Some states and provinces require more secure restraint. We have not had any problems with him other than he got into some bad water in the Yukon and was sick for a couple of days (now its bottled water for him when away from home).
BTW we use a magnetic screen door that the cat has figured out to allow him to go in and out as he pleases(except at night) really messes him up when we close the normal screen door and he just bumps it trying to get out or in.
Here is a link to Rusty's Big Adventure