I haven't made a Camaro headliner yet, but I can't imagine that the headliner can't pass through the big doors. Meanwhile I also did some models where the windshields supposedly had to be removed (VW Jetta notchback, Jaguar XJ etc) but they can also be removed without the removing the windshield. Often the problem is that the centre console is too high and the panels of the console have to be completely removed. Without a console you can tilt the headliner further and then fit diagonally through the door. I can't promise you this will work on the Camaro

I have noticed some of the problem stems from all of the extra stuff that is getting installed to the back of the headliner boards. Styrofoam or plastic to help with noise and vibration. It makes the board thicker and stiffer. Like Jens stated I can't imagine with the size of those doors and the rear quarter glass open the headliner wouldn't fit through.

I found this on a Camaro forum. Apparently it can be done. Passenger seat removed and shifter towards the rear of the car. and it will come out.
https://www.camaro5.com/forums/showthread.php?t=203826

I'll just post this here, because it fits the topic quite well. We recently had to make a headliner for a Jaguar Daimler V8 (X308), but the customer did not want to pay the extra price for removing the rear window, but asked us to cut the headliner into 2 parts. At the end I was really surprised how inconspicuous the edge above the headrests actually is. And I think it is - especially in terms of price - worth considering to offer it to the customer in this version as well.

That's a great idea. Thanks for sharing

That looks really Jens. I like the idea

So here's an update on the Camaro headliner. I pulled both the front seats, rear seat and shifted the console back and still couldn't get the board out. Although I could have forced it and bent the board but the damage to the board wouldn't have been worth it. Ultimately, I had the windshield pulled and replaced.

Other then having to pull the windshield, removing and installing the headliner board isn't difficult in this car. I wrapped the liner in black headliner suede. You'll need a 60" wide suede to cover this board but it can be done in one piece without any seams. I also wrapped the A pillars and sailpanels.

Overall it's a pretty straight forward job but I highly recommend replacing the windshield when doing a headliner on one of these newer Camaros.

Sometimes you will get lucky and the glass guy will get the windshield out without breaking it, I repaired a shrunken leather dash on a Porsche recently and they got it out w/o breaking it.
But there is always a chance that the windshield will break in the process.

I have not done a Camaro headliner, but we have successfully been able to get the headliner boards out in some other vehicles where the windshield was supposed to be pulled in order to get the board out. And there are some where we just had to have the glass pulled.
On some of them I think they build the vehicle around the headliner!