[hat_man]

Thanks Aerohead. I get it now. Low pressure under the tonneau and higher behind tailgate. I'm assuming that the cab end of the half tonneau needs to be open to the bed to work correctly. It's kind of a shame if that's true. It defeats the practical purpose of the cover keeping the elements out. Full aero cap becomes the better drag reduction/practical option, but also the most labor intensive.

Is half tonneau a figure of speech, or is it covering 50% of the length of the bed? My mind is trying to configure something that is open to the bed and can still keep out most of the weather.