I put the plate on it and a light and went and tested it.
SADLY the only straight, high speed (35+ mph), low traffic, FLAT piece of road nearby was blocked off for construction work, and I went to the next best piece of road. Which was obviously NOT flat. However I did do several runs each way, and averaged them out with hopes of getting a more realistic number.
RAW DATA:
WITH BOAT TAIL:
1 22.2
2 50.3
3 22.8
4 53.9
5 22.9
6 54.1
WITHOUT BOAT TAIL:
1 22.5
2 48.6
3 22.6
4 49.2
5 22.6
6 49.6
With Average: 37.7
Without Average 35.8
Difference 1.9 mpg
Test was done by engaging cruise control at 55 mph, cancelled with the brake, and resumed with the resume command. Readings were averaged by scan gauge II which is usually within 1% for my tank average readings.
Now to get to work on my hitch basket based detachable boat tail!
