Rear Diffusor, Anyone ever think of doing this? Options

[TonyAKAVW]

While I was thinking about better ways to vent heated air from the radiator on a subaru conversion, I began thinking of adding a tray under the engine bay area to help isolate the bottom of the car from the top. This would be for the same purpose as the engine tin with a stock engine.

Anyway, when I got to thinking about having a tray under the engine bay I thought "why not extend it all the way back?" The rear valence on 914s traps air, why not put a rear diffuser there like the Lotus Elise has? If you have a continuous underbelly to the car that goes from front to back, it seems that this might work.

One potential source of problems is the exhaust heat from the headers, the pipes that go to the muffler, and the muffler itself. It seems like there might be a way to vent out that heat, maybe some grille material on the rear bumper? Bring in fresh air through the engine bay lid?

-Tony