Dave, both materials (Lexan and stretched acrylic) are excellent.

For impact resistance I'd go with the polycarbonate (Lexan). I saw a tape a long time ago demonstrating Lexan's strength in that area. An airplane windshield was very solidly attached to a fixture in an angle similar to the one it would have in a corporate jet type airplane. To simulate a bird strike situation, chickens, like you'd buy at a grocery store, were fired from an air cannon at maybe 300 mph (a guess on my part) directly at the windshield. The windshield bowed way in, it looked like two or three inches, but it didn't shatter or even crack. Lexan is tough material!

But since the liklihood of your encountering a duck flying 300 mph while you are out on a Sunday drive is small, I'd use the stretched acrylic. It is, as m falconstein indicated, more scratch resistant than Lexan. I'm not saying stretched can't be scratched, it can, but when it does get scratched, the damage is much easier to polish out than it would be on Lexan.

I have never worked in either purchasing or sales of these products so I don't know who sells smaller amounts of these products or what they would cost, but my guess would be that a company called "Aircraft Spruce and Specialty Co." would be a very good place to look. They sell just about everything for people who build their own airplanes. I'm sure they have a website.

I have only made one acrylic window for one of my vehicles. The lovely child of one of my former neighbors (I'm certain that's who did it) was given a pellet rifle. He decided to test it by shooting at the drivers side window in a 1970 Dodge 3/4 ton crew cab I owned. I bouight a piece of 0.250 stretched from my employer and made a new one and it worked fine and was still looking new when I sold the truck.

Good luck,

Jim