Lexan would be much, much lighter.
Im not trying to argue.... Just understand.... It will not be as simple as taking out your side glass, tracing it on Lexan, cutting the new windows and bolting them in.
The side glass has a curve. The Lexan will be flat. The will never roll up and down right.
This problem can be solved in several ways but at significant cost and effort.
And again... They will just get scratched all to hell if you roll them up and down.
Go for it and let us know how they work.