Would half tubing even be worth the effort? Even if you could maintain attached flow (with no belly pan) would a radius make a difference? The front of the car is a very high pressure zone and you shouldn't have even a hint of trouble there.
It seems to me that what you're trying to do with a radius would be better accomplished by building a whole new bull nose with compound curvature and everything.
For sure duct the cooling. If you can patch that hole, it'll probably be better for aero to make it a "bottom breather" and move the cooling intake underneath the nose. This maintains clean airflow over the nose instead of breaking it up when it passes the vent.
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He gave me a dollar. A blood-soaked dollar.
I cannot get the spot out but it's okay; It still works in the store
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