[FirstOwner69]

Way back in the early 70s when the oval "retainers" in my 69 were tearing out of the carpet and the carpet was starting to sag at the top, I merely lifted the carpet up to expose the screws, removed the screws, placed a yardstick horizontally against the back of the carpet, inserted the screws through the yardstick and back of the carpet, and folded the carpet back down hiding the yardstick. Looked better than new and has remained that way all these years. The corner areas are still retained as original. For the corners you could possibly use an aluminum yardstick or other thin aluminum, cut it to length and bend it to conform to the sheet metal. No one but you will ever know. Here's the best picture I have from a couple years ago.