I was never even able to zip the qindow out of my 68 GTS. The installer before I bought the car got the zipper too close to the rear bow. Then when I had the top replaced the IDIOT did the same thing even though I warned him about it. And, that can't be fixed without replacing the top again. Never have had a problem with glass clearance. Same with my 67 Barracuda, but the zipper can be used on that top.