Hi everyone! I did quilt Christmas Wishes from the side with the deer and the house and my quilting was done to enhance that side and I figured the designs would just fall "wherever" on the other side. I quilt on longarm that is mounted on a rack and it is near impossible to line up the two sides if you had two quilts the same on top and bottom, actually one would have to be a mirror image of the other but even then I wouldn't attempt it. On mine, I messed up on my measurement on the top. I thought I had it centered within an inch from top to bottom (side to side lining up is much easier). But I must have wrote it down wrong. So I ended up chopping some of the blocks on the bottom of the scrappy side. As it was mine I didn't really care as I was so happy with the overall finish.
Anytime I have done a double sided quilt, I choose one side that is the "top" and custom quilt it for that, and let the chips fall where they may for the back. I would never attempt to line up a double sided quilt so the quilting falls perfectly on both sides. I value my sanity (what little is left) too much.
There may be someone out there in the quilting world who can do it on a rack but I am definitely not one of them. I do know it is possible to do it with a QAYG method. Easier to control where the quilting lines fall when quilting one block at a time.