would drilling a lot of small holes in the upper portion of my rear bumper help reduce drag?
i'd put them in the locations marked in red
the idea is based on the mercedes taillight vents that take air from underneath the car and vent it at the edge of the taillights to improve a clean airflow sepparation wich would not occur if the lights had no vents and where shaped as the are.
the main idea behind my proposal is that air curently being scooped up by the rear bumper would be vented trought the holes due to the pressure difference.
if nothing else this should increase the pressure behind the car, but perhaps also stabilise the airflow.
the holes near the edge of the bumper might help a little to improve sepparation there.
the holes would be in the unpained portion of the bumper so they'd be fairly invisible. larger holes with some incerts might even resemble parking sensors. right now the bumper doesn't fit very tight and looking from below you can actually see light between the bumper and the trunklid edge so perhaps air is already being vented trought there.
but could it work and produce a measurable difference or could it have potential downsides?