I don't see your photo. I wouldn't worry about structural issues if just an isolated rust-thru. Of course, undercoating hides much, so poke around. On other sites I have seen tremendous rust-thrus in convertibles yet the car is still magically held together somehow. A car with a full top is much more rigid.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans