Most types of plexiglass will fracture upon harder impacts, but it will be stronger than foam and balsa. And it would look cooler too. But, It would make the plane so heavy that it will be hard to get off the ground or will have poor flight characteristics. It seems light in small quantities, but once you make an entire wing out of it and compare it to a similar foam wing, the weight will be very different. Just a little weight saved will make the plane fly better. Now, I'm not stopping you from experimenting, but just make sure you use inexpensive stuff and be prepared to handle a plane that flies much differently than you are used to.