Agreed. maybe it's the angle but it looks like you might need to roll the lip a bit.
Here're two pickup truck designs:
I have a friend who, last century, built an egg-shaped shell on a custom flatbed with curved sides. The first one applies the concept to a pickup cap.
The second one is a grab bag. Half-tonneau cover, vertical stacks that are Coanda nozzles, and a single wheel trailer that folds down off the back bumper.