i once did a queen reversible quilt out of corduroy. talk about idiots!
what a did was this: using the batting as a foundation (in your case the batting and one side of the quilt - you decide), i sewed the center piece (in your case this could be the panel in the center of the back) to the center of the batting. that gave me the needed stitching lines to continue. from there, i stitched on the existing stitching lines and flipped. went around the center in this manner. each time the outside stitching lines were my markers for the next round. i kept sewing and flipping until the edges and then bound off.in your case, i would back the center of the batting and sew through the center of the top of the quilt. stop. from there use those lines to stitch again and flip the backing pieces, working around the center. around again and again.
this will give you what appears to be stitch in the ditch but crisper because the stitches ARE the ditch and do not wobble at all. but not as many lines. if you have smoothed very well and pinned as you went along, you can then add more lines of stitches.
i hope this helps you.
EDIT: i forgot to say that the backing would have to come apart again and added piece by piece. ooops! more work.