Did you you use plexiglass or some other product? If plexi what size?
The best product will not be the cheapest..... I've along with Bergman used .125" x 24" x 24" thick Impact Resistant Polycarbonate (AKA Lexan) from the likes of
www.mcmaster.com or other local plastic sheeting source it comes in both clear and tint and will cost you around 40.00 per sheet. Slightly costly yes but the optical clarity is superb and it will look just as good in a couple of years as it does when new, it is also very strong and will take the abuse given out from life on a bike.