Well, you're right lexan can stop a bullet (so can plex for that matter) but the key there is surface area to soread and dissapate the impact. My father, a machinest, worked for a company in the 70's that made bullet proof shields to go between the front and back seats of police cars and they used plexiglass that was thick enough to stop a .38 round. If you'll look though, I said that when lexan gets small it get's brittle and once you drill mounting holes for the shocks there won't be much material left to support the shock in roll overs and crashes.
But as 125cchyperman said, give it a try and let everybody the results. I know I'd be intrested in how it works.

Oh and Carbon Fiber is much stronger than lexan because of it's molecular structue. The stuff is designed to be strong and light weight.