So I tried your way today and still ran into the same problem. I think the problem is that little foam-pad that goes between the bag and the bike. At the front of my right bag, the pad slowly wiggles its way out from under that leading edge of the bag, leaving the textile material directly in contact with the blue plastic pod. As the bag wiggles a little during riding, the textile material is rubbing down the paint. I'll try to get a picture later for some suggestions on how to fix this problem. I am contemplating getting a new plastic for their, and the just putting this worn one on for when I use the bags.
I'm going to check to see if there's any way to move those pads around a bit or make them stay put somehow. Maybe it's just not quite tight enough? Try snugging them up a bit more even?