Hi Chris,
I think the biggest issue with the hood scoop is the pressure differential in thee engine bay. With the big radiator opening we are ramming lots of air into the engine bay. It's only escape path is the side vents and under the body. Given the shape of the front of the car there can be quite a bit of pressure under the car too with no splitter to divert the air to the sides. With all that in mind I reckon more air probably comes out of the scoop than goes into it.
The only way to make the hood scoop work it to seal it to the underside of the bonnet. A turkey pan with a foam rubber lip seal to seal it to the inside of the bonnet would probably work.
An alternative would be to run an air cleaner with a couple of snorkels on it and run flexible hoses from the snorkels and pick up cold air from the high pressure zone in front of the radiator.
This is the kind of air cleaner I'm referring to
Cheers