It's not popular with many but I do. When I started RVing with the cat I made her ride in the truck with me. She was very vocal while in a moving truck, for hours sometimes. She would often pant. I would turn her loose in the 5er during extended rest stops so she could eat/drink/use litter box. One day she went into hiding when it was time to go back in the truck so I continued the trip with her in the 5er.
She didn't seem any the worse for wear at the end of that day, or any other travel day for that matter. The cat and I are both very aware of her location during slide operation. She's either under the futon (her preferred safe location) or in my sight whenever the slides are being operated.