Yeah, creating a removable boat tail was the main inspiration for thinking up the box. I read a whole bunch of posts on here about people who were "going" to make a boat tail, but they sounded horrendously complex!
The hitch mount should take out a lot of the issues around making a strong enough structure, and would hopefully increase my economy. And if I can cram some stuff in there as well, bonus!
At the moment I have a strand of wool tied to the emblem, it's my new "draft indicator". I was quite surprised how far back the wake is on a semi - 2 to 3 seconds following distance and still the wool indicates less head wind.