https://ecomodder.com/forum/member-a...here-money.jpghttps://ecomodder.com/forum/member-a...nt-attacks.jpghttps://ecomodder.com/forum/member-a...-windkanal.jpghere's a link to a dated Mitsubishi box truck worth looking at. Some box truck at the time were near Cd 0.90.
https://ecomodder.com/forum/member-a...aero-truck.jpg
You can get away with murder at the front, but gaps are expensive, and transitions to the 'roof' need to be 'tuned'. You'll notice flow separation on the roof of the trailer van.
On the way to see the Dynaxion Car, at Harrah's Auto Museum, Reno, Nevada, I snapped this shot of leading-edge 2-D flow separation on a bridge abutment under a bridge over the Truckee River. It offers a clue as to aerodynamic challenges with 'hard' edges.
Finally, Hucho's iconic image of a squareback wake, which you'll never find used in nature.