My plans are kind of a cross between a topper and a tonneau:
www.mivehiclesolutions.com
Polarizing looks wise, but I love it. I am not aware of any wind tunnel tests, but shape alone would suggest it's about as aerodynamic as you're going to get.

Michigan Vehicle Solutions
Polarizing looks wise, but I love it. I am not aware of any wind tunnel tests, but shape alone would suggest it's about as aerodynamic as you're going to get.