It will depend on the quilting requirements of the batt you used. If you have the packaging check it, if not, it is up to you. Running a fancy stitching line down the middle sounds like good idea but unless you have your quilt perfectly basted, you may run into the problem of the layers advancing enough that you end up with a pucker of fabric. I would be more inclined to add a little quilting motif every so many inches around the border.