I'm not qualified to advise you.This is the sort of thing which costs $100,000 in a full-scale wind tunnel to figure out.
The over-the-bonnet extractors have been primarily the domain of race cars,which are more for down-force than drag reduction
Kamm placed his extractor at the base of the windshield,using the flow to help energise the flow over the windshield.
The same thing was done on some of the Jaray cars
Mercedes did the same with their C-111 III,but again,this is a 'race car' designed for down-force.
Morelli spent $100,000 or so at Pininfarina to optimize the extractors on his 1978 CNR 'banana' car.
Today,Tesla is credited for allowing 'engine bay' air to escape only 'under' their cars.
No low-drag concept cars,except the CNR car have used over the bonnet extractors.
Mine,on the T-100 will be tested open and sealed to see if they hurt things.