I added some construction photos of the topper to my profile:
http://ecomodder.com/forum/member-jr...ly-driver.html
I did a short speed run last summer at 65 MPH. Mileage dropped from 32-33 MPG to 28-29 MPG. That was the end of that test.
Finally have the summer 2011 average gas mileage with the aero topper - 34.87 MPG. That's for a total of 3771.0 miles and 108.16 gallons of gas.
Overall summary of improvements to date:
Baseline - driving "normal" - before winter 2007:
Winter: 21 MPG
Summer: 27 MPG
Dec 07 thru Summer 08 - DWL, new tires, 47 PSI
Winter: 23.24 MPG
Summer: 29.70 MPG
Dec 08 thru Summer 09 - kill switch
Winter: 24.68 MPG
Summer: 32.14 MPG
Dec 09 thru Summer 10 - Grille block
Winter: 26.78 MPG
Summer: 33.80 MPG
Dec 10 thru Summer 11 - Aero topper replaced Leer topper
Winter: 28.11 MPG
Summer: 34.87 MPG
Summer mileage is for 3 months in summer, winter mileage is for December through February.