I love a flannel backing. I finished a quilt a few days ago and used flannel on the back. i washed and dried it first, but should have washing it multiple times since it bled (red). I was able to get most of the "pink" out of it by more washing and a final wash of Synthrapol , which I should have used the first time, and will remember from now on. I'm not sure about fleece shrinking, but what the hey, why take a chance!