Well I can tell you for sure that over at the Net Reg site in the maintenance section is where I saw the tale about the "home made" rad screens. I was reading up before I even got my Z. So when it arrived that was the first thing I made using the info in the "How To" section.
In a word I'm sooooo glad I did that before I started using the car. You should see the stuff that screen collects! I feel it is sooo worth your time to do because....well it just collects all those leafs and paper. I clean mine once a week and never fail to find that it stopped something. My car only had 7700 miles w/no screen and when I pulled the rad to clean it, @ 14,000 miles, there was enough stuff in there to make me glad I made the screen.
Tom