Wow, $50? Lucky you. When my windshield cracked and I priced out Lexan it came up about the same price as glass (~$150). Are you sure the Lexan was the required thickness per the rules? Did you include the extra cost of the windshield clips and inner reinforcement bars that are required when running Lexan windows?

I would agree that the glass will chip again, however, I have 5 years on my new windshield and it is still absolutely fine. I think they will last a lot onger than you are thinking.

As another "simple solution", you could always run STU in SCCA.