I'm using some leftover pieced blocks with a lot of tiny pieces from the front of the quilt on the back, I've been thinking of putting on at least a water soluble lightweight interfacing on them to help them hold together better for the quilting part of the project. Won't make a final decision on that until I decide whether I'm going to be quilting it or sending it out. And then I will ask the long-armer what they prefer.
Usually when you are piecing backs you are using large sections and a .5" seam allowance, instead of tiny pieces and a .25" seam.