Originally Posted by greensleeves
Pin a finished edge to the takeup/back leader. Pin the backing of the unfinished edge to the front/top leader and then you can adjust the batting and top as you continue to quilt. Pin a little beyond (toward the front) where you will be stitching through all three layer to help stabilize if you want. Otherwise just let the batting and top "float". In this situation you will not be using the leader that you would normally pin your backing to. Hope this helps.
You may want to stabilize the quilt top first by basting with the LA down each side. I've found the side basting well worth the time with some quilts I've done.