[elhigh]

My '87 Toyota has a cab-high topper, it's almost exactly the same height as the roof of the truck. I noticed a modest improvement in fuel economy when I installed it, about 5-10%.

For various reasons, storage space chief among them, the topper stays on the truck about 99.44% of the time. It only comes off for very large construction projects or major firewood opportunities.

If I ever find myself in that magical confluence of surplus time and surplus money, I would like to make a nice whaleback topper like others here have made. With careful driving I can push 40mpg, I think with a whaleback I could hit 40mpg even with careless driving.