Convertible rear windows I feel you brother. That is way more common I find with plastic than glass.Older Mustangs drive me nuts so I try to convince my customer to use glass. One trick a guy showed me was,assuming the window is installed correctly. When you are installing the top and every thing looks mint except the top has now created a little looseness in the window.. Now the wireon has not been installed at this point. Draw a line on the front edge of the wireon bow where the top is laying. Open the latches and pull the rear bow up until the line you drew is in the center of the bow. Staple across. Lock latches.This will pull the whole rear window curtain up and get that little pucker out. Always remember though we are our worst critics. I worry about things that all the time that a customer never mentions. But wrinkles in tops bug me so I try to do it right.