I don't run a screen, never found any real need and in my experience it does impact flow and response

 

I run with both screens, the "foil" i was talking about is something like this:
only shaped to work as a duct when working at speed.
With the last bend cut straight and the filter hanging vertical it makes a little difference. The lost flow to the radiator is quickly recovered elsewhere.

 

You've gotta believe me...