Checked today. A friend with GLC. Yes , it's cardboard.
Sorry I did not take a photo , but I had my phone on charging. But will make a photo next time I will see him.
And he even has the panoramic roof ( I initially was thinking that this was only on the normal roof )
It's not on the liner ! It's between the liner and the metal . More exactly , glued to the metal sheet
Will come back with proof (picture) . Sorry , I did not have my phone with me
Ok, and tell us what the compromise is if this is true? And if others do this, are they as deficient as Mercedes?
M