Bill, your idea has sound properties but in practice it's not very workable.
What part is not workable? I plan on cutting two 10" X 18" panels out of the very back of the fiberglass hood (the back of the hoof will be the back of each panel), and attaching them to the rest of the hood, where they were cut from, with two 18"-wide piano hinges. Air pressure (if there is any) will raise them in the back, at speed, and let the trapped air out, decreasing drag.
I'm not that concerned about heat, or cooling, sitting still, as this car will not see much street driving.
You could put a small cowl scoop on it and just leave it open,quote]
I am trying to keep this thing looking like a bone stock 4-door sedan... LOL!
A hood scoop of any kind KILLS the stealth... Nobody's gonna notice a low-lying piano hinge.... Methinks...