I sold a car recently and intended to use the proceeds to replace the stock bumper brackets with a custom built class-1 trailer hitch on my 1971 SuperBeetle, to pull a Westphalia utility trailer. This would incorporate heavy-duty sockets for the bike rack that could double as mounting points for a single wheel trailer and tabs to mount the rear bumper. This would give me three options in back. Unfortunately, I had to come down $1550 from my asking price to sell, so the custom hitch isn't happening.
We now have two data points that show how slowly my thought process works. In
an earlier thread, I posted this pic after staying up all night to model the idea for a retractable boat-tail for the Type II panel van.
Today I used some random parts to mock it up in full scale on the Gold Bug. So, 2 months to go from a model of an immobile vehicle to mock-up in full scale on the weekly driver. I used a tow bar that normally mounts to the lower torsion bar housing in the front of a Standard Beetle (it won't fit a Super with its Macpherson struts), as an single-wheel trailer A-frame. The [hinged, castoring, heavy] trailer wheel might be optional. If it's not used for cargo it could hang from straps from the bicycle rack, be stopped by a block below the hinge line and/or sprung with the fiberglass rods that would form the aero shape.
I haven't said much yet about my gas mileage. With the previous car [same year, make and model] I took it from 17mpg, as received. to a best of 30mpg. While I had both I did some coast-down testing, and where the older car shed 20mph in 24 seconds, the new car only needed 21 seconds. Recently I gassed up. drove 106 miles and refilled. 6 miles at freeway speeds and 100 miles in convoy with the VW club at 55mph. When the car was new 95,000 miles ago it got 26mpg. At 55mph I got 21mpg. And that's with the electronic ignition that made ~4mpg difference on the other car. I'm going to have to dig myself out of a hole.