[lunarhighway]

autospeed had a great article on bonnet vents.

however i'm inclined to think from their results and from the placements of functional vents on production cars half way the hood is a better place the pressure difference with the front is much greater there than just ahead of the windshield. the back of the windshield is generally the place where the interior cooling air INTAKES are.

perhaps raising the hood at the back might still work because of the sheer size of the resulting gap, but relative small extractors early on the hood can do the same thing