For your amusement:
https://www.youtube.com/watch?v=ngTk1Znxp_Y
Me over 10 years ago taking my first Cobra for its SVA re-test to legalise it, prior to paint and a few add-ons for the purposes of the test. No top or side curtains of any sort. We were the only open top sports car OTR that cold October day, although we got a lot of thumbs up from people that must have thought we were mad. 140 mile round trip in pouring rain around the M25 - London's orbital motorway and out onto the motorway in Kent. Tremendous spray from passing trucks, I was fairly scared as visibility was down to less than 5m as I peered round the screen, given there was more rain coming round on the inside than on the front of it.
Moral of the story: never drive a cobra in high rain high wind conditions on a freeway/motorway without some form of top. Too dangerous and car took weeks to dry out.