I`m towing a different boat , a lighter one and I lost 1mpg.
8mpg towing Bad Kitty, 9-10mpg towing Care Diem the cig.

You guys notice if you lost MPH after putting these on or is it just wind resistance??

I have not lost any mpg's running my rock tamers vs not running them pulling any of my boats. I would say its the wind resistance of the cats larger profile vs the v hull. I'm far from an expert, but that would be my thoughts.

That makes sense.. she sticks out past the truck where the cig was all behind .

Yeah wind resistance has always had the biggest effect on us more so than weight.