From the Way-Back machine (Oregon coast, circa 2006, when I owned a real SMB before (regrettably) selling it to work abroad):
Please note that this is when we weren't in motion.
In motion, Zacky (80 lb. driver) sprawled on the RB50 sofa. Tory Ann (65 lb. shotgun) curled up on her shotgun seat (unless she wanted the sofa, in which case she stared Zacky into submission, and because he didn't fit on the shotgun seat, he just lay on the floor or stood between the seats, unhappy.)
[That said, I acknowledge that I was being irresponsible since they weren't tethered or crated. They had really good car manners, but nonetheless in a crash could be thrown and severely injured. In my daily-drive Explorer, they always rode in firmly anchored crates.]
Also, my first homebrew van (1995 E150 RB cargo van) had four large crates (earlier Weimaraner generations) bolted in with the bed on top of three crates running lengthwise behind the driver....