As a newbie to older chevy trucks, I have been most impressed with the products I ordered from Chevy Duty and the speed with which they were shipped. Now I am trying to replace a vent window seal on my '87 full size and can't figure how to get the new seal into the upper corner. I have the window removed from the door and the glass removed from the window frame, but the seal does not want to slide all the way up into that corner. Any help out there???????