I can report that my truck, while towing 8000lbs, has been getting, on average 20L/100kms. Which is about 14mpg.
With the Smarty Jr installed, set on fuel economy, it has dropped to 16. 3l/100kms or up to about 17mpg.
Not a scientific test, but an improvement for certain.
I think I'll set it on "performance" and set POD on about 50 or 60%.
I have a 500 mile trip next week (with no load), it will be interesting to see what mileage it gets.