Quick update---finally got my license plates in, and installed them.
I plan on mounting a small additional grille block piece behind the license plate, leaving two smaller "nostrils" open to make sure it's ventilated, but as aerodynamic as possible.
I made it kind of high-contrast so you can even see the grille blocks on camera. Difficult to see otherwise.
So I suppose next up is the center piece. I'll permanently mount the license plate soon (need to buy correct screws with nuts), and will also mount the central grille block to the backside of the plate at that time too.