I can relate to the frustration - why don't you make two quilts out of it - they are both so gorgeous -
I'm sure you've done this over and over, but have you measured the lines on the top and back to make sure that they are lining up the way you want them to?
I was thinking about trying to make a pieced back for a quilt top I just (finally) finished, but was concerned about trying to line it up properly - I did one years ago and it's about 1/4 inch off - I think the only person that is "aware" of it is me, but still - - - -
You said you are doing stitch-in-the ditch - that's not very forgiving for design lines if you are trying to match the top and back -