Over in "Prius Technical Stuff" there was a posting that removal of the rear spoiler from the NHW11 (2001-03) model reduces mileage. Furthermore, there is a slot that runs across the bottom with what feels like a 1 cm, rectangular shape. I suspect this slot generates a linear vortex to improve the efficiency of the rear 'wing.'
It is a good question: does the flow reattach? I need to tuff the top of the trunk to see what is happening.
Right now, it looks like a dozen of the
Airtabs would keep the flow attached to the rear window. The question is whether or not it might cause something else to 'squish out.' Still it might allow removal of that rear spoiler without an increase in drag.
Most rear spoilers are there to increase down-force for road racing. Somehow, I don't think there has been much discussion about drag reduction.
Bob Wilson