I was the first to use Garry Hall's flush mount kit. It was intended to have round corners and he gave me a short piece of the rubber to make sure it would fit and the groove was the right width. Unfortunately Garry was out of town when they did the installation and instead of using the rubber I was given, they used vinyl which puckered a bit. Bev Hall said they tried 3 times to get it right, but who knows.
Here are pictures of the upper and lower corners (complete with puckers, which I plan to eliminate one way or the other). The seam is in the lower middle. The width of the vinyl is 1/2". Also, I don't know how you could use the std rubber with the glue in windshield as the rubber is meant to go around the windshield. I suppose you could cut off the back half?
Finally, you should be able to get the rubber at one of the vendors. Have you tried Wilkinson? Also, if you end up not using your roll, I might be interested in buying it.
