Front Convertible Top Seal for '63 Dart

Find an opening to the inner cavity of the weather-strip near the corners and see what you can stuff in there to build it up. The old trick is to get the corner at the A piller+window glass to clamp across to seal. It's a combination of adjusting the pressure of the header clamps, the forward pressure of the side seals without splitting the rubber.
I have used rubber fuel hose, blocks of silicon rubber from antenna shock mounts, and foam weather-strip from the hardware store.