I think those aero caps would sell if you had decent production and marketing. Just my personal opinion, I think that first design with the flat shoulders would look incredible on a sport truck, lowered down and a few aero tricks, I think that would be cool! For aero and function, your other designs look awesome.
I see what you're saying about the width differences from the top of the bed compared to the sides of the truck. Here is what it looks like set at the width at the top
Compared to full width:
I'm shocked, I had no idea that the tapered in that much at the top of the cab. Now I'm wondering if that is just this generation of truck, or all of them. Now I want to see one on the road to take a closer look at one.
Of course this is all assuming that I've applied the template correctly, if I have not, I will gladly accept criticism and advise on how to do it better.