Nah. It is a twin-size foam mattress, rolled up in a bag. No aerodynamics there.
I drive a pickup all the time, and I’m afraid of tarps too. I tie down floppy or big stuff with trucker’s rope to the point where it takes longer to untie the hay than it did to stack in there in the first place.
But if you’re worried about your luggage getting wet, I’ve thrown mine into big plastic trash bags and duct-taped the snot out of each one, and that’s brought me through surprise rainstorms just fine. I throw stuff up towards the front of the bed, where it’s not as windy. If it’s as heavy as my luggage is, it shouldn’t fly out. Overpack!
You could also buy a cargo net, which looks like a giant spiderweb of bungee cords. Lay it over your load and either attach it to the bottom cleats that the truck will surely have, or over the top if the load is tall enough. Keep it close to the load though.
Am I mistaken, or aren’t sofas and such packed in plastic when shipped to a furniture dealer? I always thought they were in large bags, which were then taped down taut. Maybe a call to a local furniture store will be helpful – perhaps they’d have some excess wrapping you can use.
I’m also wondering if one can’t buy huge visquene (sp?) bags at Home Depot or Lowe’s? Going down a bit in size, I’ve bought huge, thick, black “contractor bags” from home centers that are big enough to fit over about half of a regular-size sofa. Maybe two of these taped together would do the trick? A third bag could be cut into a tube shape to serve as a joining piece if the sofa is especially long.
All of this makes me reflect that pickups are good for stuff like sand and gravel. If you’re moving stuff that shouldn’t get wet, a van may be better.
We’re sadly aware that a van would be better. Oh, if we could get an acceptable van! Remember the 75" sofa plus three people, for twelve hours, caveat.
Why not use a trailer?
Rake leaves.
Fill pickup with same.
Enter parkway and accelerate to 55 MPH.
Don’t look in rear view mirror.
Get off first exit, and go home.
It’s like magic, I tell you…magic! 
You guys are paranoid. I could see the use of a tarp in case it rains or snows, but anything of weight in a pickup bed will not fly out. Suitcases and bags and such will stay put with nothing else needed.
Beltbuckle: Indiana to New York. December. Rain in forecast. Waterproofing needed.
Dag Otto: we just came up with that brilliant idea ourselves. We have to have a hitch installed… and none of us have ever driven a car with a trailer attached.
Any way to rent a truck with a cap?
Or is your load too tall?
Wrap your luggage in the tarp and secure the tarp with rope. Lay it down in the bed.
Go to Wal Mart or wherever and get two trucks straps with hooks at either end and the self locking/adjustment. Run the straps criscross over the bed and secure on the corners under the rails. Pull tight.