My next big quilt I do, I will the 2 halves and then join them. I will quilt both halves leaving 2 inches unquilted down the center on both halves. I will then join the 2 top sections down the middle by machine. I with trim the batting to meet down the center of the quilt and iron on batting join tape. I will then iron one side of the back fabric over the join and overlap the second piece of the back. I will pin it and ladder stitch the back seam. If everything looks perfect, I will quilt the last 4 inch section down the center of the quilt.