so i have a 1996 Coleman sun valley popup . My interior Ceiling has a bunch of stress cracks and is sort of sagging (not to bad ,barley noticeable . The stress cracks and sagging is NOT due to water damage .. The ceiling in my popup is made of this pvc almost plastic material witch i believe is about 1/8 .. I would like to replace it the whole ceiling but the 1 thing that scares me is that the corners are rounded off ,most popup that i went inside and looked up have square edges ,mine are rounded at the corners . With that said even if i get 1/8 luan sheet i know it would round out on the sides but what about the corners ?? Anyone have any ideas or know /seen what type of ceiling im dealing with ??