I do tow, some. Three different trailers, a car 4 down, a small 4x8 golfcart trailer, and a 24' enclosed. Good news is the hitch ball ends up about 24" from my zero line for a tail. A 36" tail will fit nicely. I envision it as a three sided tail, being open in the middle. Could leave the hitch alone, still be able to put bikes on the back "inside" the tail. Measurements have been taken, sketches have been drawn, etc. The Monaco Vesta has a very small tail, still waiting on an email response on how it actually works. There's an RV show in a few weeks, there's usually one there. I might have a tape measure in my pocket...
Cool thing is that I can remove my current rear cap and fab up a trial tail. See how it works, both in aero/MPG and towing impact. The enclosed trailer won't really benefit as the tail will direct air right onto the front of the trailer, but I don't tow it much, and it would be a bit of a gap filler. I can put the OEM cap back on if it doesn't work out. Or modify it if it works. It's already fiberglass, and very close to square. A single mold could be made that three pieces could be pulled from, 2 sides and a top. We'll see, one step at a time.
If this family could build a whole RV in 4 months, I can build a tail, right?
(They used boat building techniques. Folks could use the same methods. I know a guy who builds racing hydroplanes, planes, and racecars. I'll surely be visiting him to see what he would do.)