I was reading Eric's great write-up in the classic threads about re-installing the rear glass and he mentions there should be two rubber pads beneath the glass. There weren't any on my car. Maybe that's why it never sealed fully.
I'm going to make some up, but does anybody have a picture of what they look like? The thread said around 3" by 1/4". Thanks

When I bought my butyl tape/rope it came with rubber blocks. Here is a picture of a windshield spacer, pretty much the same thing - pelicanparts item 914-541-907-10-OEM

Great picture! Thanks

It's nothing but a spacer to locate the window .... just like a windshield install. The window is held in (hopefully) with butyl tape.