Ripping those seams out is easier if you can get between the two layers. IN other words open the side up and then work along the stitching from the inside of the bag. Pulling the two halves gently apart before slipping the seam ripper in there. That will make it easier to get the thread and not your fingers or the shell fabric.
Yeah, where were you last night at 5:30 Eastern Time when I started? That is basically what I did after about 10 minutes of trial and error. The nice thing about old equipment is that the thread becomes a little brittle. There were many stretches that I was able to gently pull the nylon and the stitches would rip for about a foot or so once I got it started; loved that.