We just returned from three months on the road "snowbirding", traveling almost 5,000 miles with our two "kitties" (Bubba is 20 lbs....yikes!) and they did all their traveling in the bedroom of our Sundance 265rk 5th wheel.
My DH made a wood step that fits right on the first bedroom steps and the door rolls right over it....viola, the cats are safe and sound in the bedroom!!
We leave their litter box and a small amount of water and dry food on the floor with them, and every time we stop we check on them with the same results.....sleepy eyes, and the expressions of "are we there yet?".
We keep the MaxxAir vent open and they did just fine.
We always leave the cats in the bedroom until we have stopped for the day (we very rarely travel more than 5 hours) and have put the slide out. I always have the fear that a cat, any cat, would somehow find a way to wiggle into or out of someplace next to the slide.....so, if the slide is in, the cats are locked safely in the bedroom.
If anyone would like to have pictures and such of that step that my DH made, I will be happy to pass that info along.
BTW, we could not imagine traveling without our little furballs.....they seemed to love each new place and new smells, we would put them out in a large cage on the tables and people would always come by and they loved the attention!
Enjoy!
Rick and Janine