I don't use flannel on my backings. A lot of the times, it is woven much looser than cotton and therefore will fray and pull out much easier. That being said, it is much softer and will stay on your lap better, but unless I would use a very good grade, super heavy, I would have no confidence in it's staying power. Too many years of having flannel shirts deteriorate after washing just a few times in the washer, whereas cotton goes on forever. Every once in a while I find a flannel that I think will last and it's always pricey. If I did use it, I would probably double sew all my seams. The first being at the 1/4 inch mark and then a wavy seam that goes from 1/8 inch to 1/4 to prevent it pulling out. That's what I have done when I made the mistake of buying just the right color fabric and didn't realize about the fraying until I just didn't want to take out all the seams and replace the fabric.
Edited to add: I was looking at your picture and it looks like some of the seams aren't a full quarter. That would have contributed to the pulling apart of the seams.
Last edited by Barb in Louisiana; 04-02-2018 at 07:18 AM.