That's a very interesting accessory, Frank. I suspect 110lb is the capacity, to weigh that empty it would be made of 1/4" plate metal.
Look at this:
Even people who *are* thinking about the aerodynamics use those square end caps and don't think about the air flowing off the drip rail.
I looked at something similar. I use the '58 Canadian Beetle as a 'chicken coop' to store bumper and seats, and it has this cargo pod on top.
I positioned it as a boat tail, replacing the engine lid, to see how much I'd have to chop out for engine clearance
I forget that angle but it looks like ~22.5° to me now. It would need a pie-cut to give it adequate plan taper; something I haven't chosen to do yet.
Ron -- What will it take to get it running?