I'm not sure the question being answered is the question you asked. Do you intend to make a big envelope, with the top part quilted, and stuff it with cedar chips or something like that? So the bottom of the quilted part will never be against anything but the cedar chips (or other stuffing)? If so, I would forget about batting altogether. If the reason for quilting the top is that it will be pieced, then I would put a backing under it (any fabric at all), but no batting. Or maybe I don't understand the question either.