I use a Ford Transit Eco Boost,high roof extended length. Let me know of any questions that might help you. Couple of shots of my set up. Van is in shop now. I'm having skid rails/guides added.
Cruise is always set between 62-65. I've seen the dash display mpg go as low as 13.5 and as high as 20 mpg. Just depends on load and conditions I guess.