So is this a Bonneville design only issue or an H body design issue?

Mine doesn't seem to have rust around the filler neck, or in the metal where that supposed drain hole is. I'm not exactly sure what I'm looking for, either though. Is it something you can catch early on and fix it yourself, or do you have to wait for some bad symptoms to appear first?

nope have seen it on park ave, lesabres, GP, lumina, Impala, basically the whole line

Mine was not visible until the paint bubbled on the exterior of the body. By then it was too late, a hole had formed below the paint. It started on the inside in an area that cant be accessed I think. It seems to be present everywhere the inner fender contacts the exterior body panel on the gas filler side because I have a hole forward of the filler, but also signs rear of the filler. Has anybody repaired this themselves? I'm contemplating starting it soon, but am a little leary of cutting and welding near the fuel filler area...

Must be a GM tradition. My 84 Camaro did this just the same and by the time I noticed it come through the body, the subframe was gone.

Took a pic today, pulled some more of the loose rust off. There is indeed foam tape between were the inner fender meets the body panel. Will probably attempt to tackle this on thursday. Cut out the bad, fab a panel and weld it back in and primed. Anybody have any recommendations, tips or suggestions before I begin?

POR13 is the best rust/bare metal primer. It is expensive but worth it. Brush it on and paint IIRC within 4 hours.

Yeah, I have been looking at inhibitors to apply in the area because im sure there is no way that I will get all of the affected areas cut out. I also plan on removing as much of the foam that I can and try to replace it with seam sealer. Going to be quite a project, I'm an amature at body repair....looks as if it will be a learning experience.

Make sure you us POR or it will rust again, I've tried several types and this is the only one that works!!!!!

hell if you have to pour some into the holes to help cover the existing rust..at least i would