The rear glass was pretty bad when I bought my 2006 roadster in 2021 (I have a 2007 coupe also). I purchased a new top made from the original German material by a company in South Carolina. Going through an upholstery/top guy the new top cost me $850, and $500 to install. If I had purchased the top myself directly the price would have been $$1,250 + the install cost. The back window separation problem was solved by making a V or C shaped "channel" for the window to be glued into so that it cannot come loose and has a lifetime rear window warranty. I had always thought that would be the way to do it and low and behold someone else finally figured it out. As an aside, I followed instruction by Top Hydraulics in Florence, OR, and uninstalled the hydraulic cylinders myself and sent them to Top Hydraulics to be rebuilt with better materials and seals. They are expected to last 35-50 years now.