I was thinking the top was shrunk up on the sides til he said between the glass and the top so I'm thinking he means between top frame and windows. But hard to say.
Age will shrink them up also. You bring up a good point though Gordo. It's not good to leave them down for long periods but if it's cold and they are old they don't go up to well then either. Just like people.
The rear windows in the '64 I've heard some say they never unzip it when they put the top down. I was told to unzip mine when I first was around the car before it was mine and think it's a good idea and sure beats replacing them as when I did have a top sometimes the glass would sit on the edge of the back of the seat and I'd have to push it back to make it fall in the package tray area. I've heard of others breaking thiers by puting the top down with window still zipped in. Heck I'm cheap and rather be safe than sorry and it doesn't take that much effort to do.
Let us know for sure which area you are talking of on the gap. One of these replies should be it though. Can't think of anything else.
'67s have the tension cables also, not sure what they do though exactly. Mine only has short bungees basically that keep the pad pulled down on the sides.
Deb