It is darn near impossible to line them up exactly on the LA. Also the back needs to be a mirror image. IOW say the top right corner block is a star and the top left corner block is a 9P. For the quilt on the back the top right must be the 9p and the top left must be the star. If not they will never ever line up. About the only way I know of to do a double sided quilt that the back and front are the same is quilt as you go on a domestic where you are quilting one block at a time. Virtually impossible to line up on a LA rack. I would not even consider doing one unless the design was an all over E2E and even then it is very hard to get the two to line up perfectly.