I'm that guy that keeps pulling the string when it comes to his cars....
I started knocking undercoating off the bottom of the car. I wanted to stop at the seam where the rear passenger foot well pans meet the sheetmetal under the rear seat, but the vibration of the needle scaler would knock loose undercoating up to 12" ahead of where I was working so I ended up removing all the undercoating. The needle scaler has a way of finding the soft spots. The cabin floor pan had looked so good prior to removing the undercoating but now showed pin holes in both front floor pan troughs where water in collects. The worst damage was under the passenger seat, which seems very odd. I called 521 Restorations and ordered a full set of cabin floor pans. It's overkill for sure, but I've come to hate floorpan patches when I can remove and replace the whole cabin floor so easily. Tomorrow I start removing the cabin floor pans...