Topper MPG Question
 

I'd like to hear from owners that have a camper shell/topper on a F350 crew cab short box. I've done a couple of searches but didn't find any info. I'd like to know about the fuel mileage with the different toppers out there . I'm about to purchase a topper (SnugTop XTR) and would like to know if I will loose MPG and approx. how much ?
A. Topper that is flush with the top.
B. Topper that is taller by a couple of inches.
C. One of the taller toppers?