I'm with Franco, I think Cees is referring to the rounded corners that should press on the trunk area? Its so tight in the boot that I'm amazed there is enough room to turn the corners under!
I too, have stored the top down for years, only the corners curl temporarily.
A BIG warning on putting the top up in cool and especially cold air: The window will crack as though cut with a knife. 1st time I was camping in Coloma, drove to the hills from the Bay area through the hot valley, with the top down, I used to slam the back down because the top is tight and I had no fear. It was jacket weather and getting dark when I closed it and I didn't take notice of the window, next morning I thought a vandel cut the window during the night and it just never made sense. Next time it happened, to my horror, the crack appeared right away. A heat gun might be a good idea for an old window coming out of a rather cool car. That may be why the next generation has a cable accross the window.