[aerohead]

My archive produced some data germane to this concept.
Only a few vehicles have ever had their pressure profiles measured and reported, or tests conducted which would illustrate any propensity for passive flow conduction.
* John Simonson's 188-mph 1953 Studebaker land speed record car incorporated rear quarter-panel-to-wake ducting, below the taillights, however no quanta has ever been provided as to the efficacy of the modification.
* Simonson's car also harvested underbody flow, via six, mandrel-bent tubes, which passed upwards 'through' the body, to under the backlight, ostensibly for drag and lift reduction.
* Simonson also tapped engine bay air at the transmission hump, and ducted it horizontally, through the cabin, exiting behind the doors.
* Dr. Alberto Morelli and Sergio Pininfarina's, 1961 Ferrari 250 GT indicated for flow reversion, a fail.
* The 1971 Lamborghini Countach LP-500 prototype demonstrated flow reversion, a fail.
* The 1973 Dodge van failed a drag reduction, under the most optimistic conditions of 100% forward stagnation pressure impelling the duct flow.
* The 1984-1987 Honda CRX produced flow reversion, a fail.
* The 2000- on, 1st-gen Honda Insight indicated for flow reversion, a fail.
* The 2018 Jaguar XE indicated for flow reversion, a fail. In order to move air from under the Jaguar to the wake, an 800% pressure rise would have to be overcome.
* Dr. Robert Englar, of Georgia Tech University's Research Institute has never been able to impel airflow without a powered prime mover.
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I'm going to hold to my original recommendation, not to pursue the 'Aero Duct.'
I wouldn't waste any time taking pressure measurements either.
I consider the project dead-on-arrival.