I tend to travel a good amount for work, and when I do, I often drive a lot of different vehicles. One of my least favorite exercises is figuring out where I can stuff suitcases into a pickup truck. Do you put them in the bed? What happens if you hit a bump, or have to swerve suddenly? Will they be safe there if you park for a bit? You can stuff them into the cabin, but then you risk hurting your upholstery and you lose seating space. Who wants to do that?
