37_GC,
Go to home Depot and get some heavy building paper first. It's about 1/2 the thickness of the cardboard. you can double the thickness if you glue it together with a spray contact cement. Use your headliner cardboard and make a pattern. Then you can try that before you mess up your cardboard. Like most of us, you will mess up quite a bit.
Check out my message from before. I would appreciate it if you would let me know if it was helpful and what procedure you used.
Mike
Last edited by Rabaut; 05/02/2023 1:32 PM.