Ive gotta agree with mojo on this, and iirc Field Motorsport done a test on bonnet raisers and they don't draw out any extra air... The vents might be better as tested & developed by Ford, they might draw air out from the rad area allowing a higher airflow.

Joe - If i were you get it setup and then see how it goes!

On the subject of antifreeze/water ratio, ive ran various cars over the years with just water for a few days at a time and the temps remain the same as with antifreeze in there... Altho maybe on a highly tuned engine antifreeze might keep the temps down but i don't know!