Your quilt is really adorable. I like to use flannel for the back of baby quilts - soft, warm, won't slip off, etc. but have never done BOTH sides in flannel. I can see where that might be a little "shifty" for you. My favorite use of flannel is for lining things - crafty projects, bags, runners - and I make sure to pin like crazy to keep things square. It looks great to me!