I have mounted a Valentine-1 right smack in the middle of the
windshield.  I have had the V1 on a Corvette and a Z-28.  In 5 years
and 200,000 miles, no tickets.  Response in C-4 seems to be as good as
in other previous vehicles.  If you're worried about it being seen,
you can get the remote read-out.

PS - hard wire it.  It tends to drain too much power if allowed to
stay on via cigarette lighter plug.

- Mike