First choice would be folder...that being said.
I used to drive a full sized crewcab dually for work. I ALWAYS kept a bike in the back for use as a dinghy or for emergency use. Usually the bike was an old beat up Raleigh 3 speed. I didn't worry about laying it flat. I wanted grab and go. However I did keep it locked down with a long cable lock. Oddest thing to ever happen, came out of a store where I had been shopping and the bike was laying half out of the truck. Someone had tried to grab and run with it...made it as far as the end of the cable. Shortened it up after that and added a second one.
Got downsized to a regular sized truck, still had to haul the same amount of company crap, went to a Raleigh Twenty folder that could be tied down on top of the tool box. Went that route for about 3 years. Just got downsized AGAIN this time to a Honda Accord sedan
I am in the market for a Brompton. I have a trunk mount rack that I put a full sized bike on or I put a sheet in the back seat and haul my Twenty along.
Aaron