I am moving a friend and her car to NY, and to get enough volume and length for the furniture we built a plug and extension on my short bed truck and plopped the canopy on it. I'll be towing her Subaru on a Uhaul car transporter behind.
I will put a shield in front of her car for dings and weather, 65" wide and 55" above the ground.
The extension over the tailgate is 66" wide and about 66" above the ground.
One thought I had was a box fairing 4' deep from the back edge of that to just over the shield in front of her car, and with shortened sides that would allow for the trailer to pivot underneath it. It would keep the rear boil down.
I'd love to do something up front. It would depend on duct tape or similar, an the difficulty is the width difference. It will be difficult to craft something that a side gust won't rip off, getting under it from the side over the rear door.
One look from this angle and the rig named itself:
I sloped that rear lid for weather runoff, leaving 36" interior height at the back edge for an 8' sofa that set the long dimension.
We crafted it with salvaged form plywood from the 2013~14 SR520 floating bridge project. That stuff has been used and re-used several times. The sides are double wall, wrapped around 2x's in the stake pockets and solid blocking at the top edge. I shot some screws with fender washers through the canopy into those edges, and ratchet strapped it down to the bed tiedowns at all corners.
I have caulked it everywhere and painted the wood with some really old paint that still stirred up.
I do have a 4x8 sheet of coroplast for the rear deflector.
When I get back east I will return the trailer, and tear down the sides and put the canopy where it was designed to go for the drive home.