You stole my idea.
Actually mine will be on a sedan, which will make it easier... but it's still going to be a couple of years before I get around to it.
I added a hitch receiver a few years ago to my civic to get a cargo rack in my slipstream, which had the benefit of having 0 impact on FE. Then I learned about boat tails and realized that's the next step.
Looking forward to seeing your results.