A recent Tesla Cybertruck range test revealed that the electric pickup truck can lose in the neighbourhood of 25 miles of range just by opening the tonneau cover. Add to this the additional weight that's likely to be on the bed when the cover is open, and hauling with the Cybertruck starts to seem rather impractical. https://www.notebookcheck.net/Cybertruck-s-surprising-efficiency-slips-with-open-tonneau-cover-at-least-25-miles-of-range-lost-at-75-mph.815431.0.html
Expected behaviour when aerodynamics are altered. Why do you think driving with all windows open at high speeds reduces efficiency?