They all get the cardboard sail panels. All my 70 and 71 cars had the cardboard. And I stripped many of them. You have one they are the same for both sides cut them out of a better material.
Unfortunately, I don't have any. All I have are these (see pic).....They fit in the same area, and are covered with headliner material. Do you think they will suffice as a backer for the new headliner?
I see that Classic lists a whole bunch of different types for the '71 Demon.