History lesson?
We've been using clear plastics for what, 80 years? in aircraft....and other than the odd ultralight trike windscreen that may flip or hit something, lexan is just not the right material.
I'm not a -12 builder, but it looks like the flat wrap is well within the manufacturers specs for 2 or 3mm plexi....so it could have been spec'd here, not necessarily a formed piece.
Van's choice may have been sound, for their reasons, but it doesn't make it a good long-term solution.
ANY Lexan I've used, when cold formed to a bend, eventually crazes, yellows, and then you can't see thru it, especially at the angles in this cockpit arrangement.
Lexan was designed as high-impact flat glazing, has moisture content, and it's properties all change for the worse as you expose it to sun, air, grit, cleaning etc.
I hate to say it, but I"m finding a lot of content in my -9a that I have to question. Seems we are throwing away the Van's part, and buying a better one later, time and time again ( instruments etc.) would I buy a kit if it was $5000 more? maybe not....but it seems penny-wise, pound-foolish.