Pretty sure I will be wrong here, but, maybe this is one of those times you would sew your outside edges together and turn inside out. I think they call it "birthing". If you do it like that, I wouldn't try to machine quilt, I would tie the quilt at the suggested spacing. Tying won't take up as much fabric. At least I hope this works, as I am going to try it myself, for the same reason. !!LOL Ladies?????

Clem55's suggestion will work. I made all of my first quilts this way (even queen sized ones) and it is probably a good way to start. Make sure both layers are the same size, stitch right sides together leaving a 12" turning space, flip inside out, stitch the quilt opening shut. Smooth, flatten and pin really well and quilt from the middle out smoothing as you go. The quilt will need no binding as all edges are now inside and secure. You can top stitch around the outside of the quilt to give the illusion of a binding. My kids used quilts finished this way for years. It's just now that they are getting the other kind.

Great idea Clem55. I can't see why that wouldn't work.

If you're going to tie your quilt, that is exactly how you would do it (although you CAN bind it after tying instead of birthing it). Machine quilting always distorts the backing and you'll end up needing to trim the top when you're done. With hand quilting, you have a little more control and it might possibly (maybe) be able to be done with the back the same size as the top. But I don't believe it would work machine quilting it.