It will slip off your bed. I would use a good quality of flannel for the backing if it was me doing it. Sounds like it will be a beautiful quilt. Hope you post a picture of it when it is finished. You could wash & dry the batting to make it shrink before putting it in the quilt. You do not have to use detergent when washing the batting. Just running it through a rinse would work & then dry it for the shrinkage.