You already know that..."Based on the Civic platform, the Del Sol was the successor to the popular Honda CR-X."
Lexan might not be perfect. True. But check out how they attached it. They put two tabs on each inside edge of the C-posts and used Dzus fasteners.
Fiberglass might work for this Del Sol, and I think you could just blend it in to the plastic trailing edge of the roof/C-posts. I'm not sure how that part bolts on to the Del Sol, though. You'd also have to deal wit the trunk.
Does the trunk on the Del Sol open forward or backwards. I know there was a motorized version that opened backwards. Maybe you could use those hinges and build your Kamm tail on to the trunk lid. ???