Most pieced backs do not attempt to mimic the front in terms of size of blocks or positioning the blocks so that seams are the same on front and back. The ones that do are usually QAYG, which makes the lining up easy, but that's not what you're attempting. It is more difficult sewing through the additional seams in the back on a DSM, and practically impossible to line up front and back on a longarm. Good luck!
I piece my backs most of the time, but I haven't done what you're describing. A couple of examples -
http://www.quiltingboard.com/picture...k-t216883.html
http://www.quiltingboard.com/picture...in-t23612.html