is there a rule for grain wise for the back of a quilt? i mean does the fabric really need to be going the same way as the front? instead of buying mor fabric to piece the sides to be wider, a friend told me that i could fold the fabric in half and cut then sew it. this way i would have the width as my front piece. i would have a seam in the middle on the back but i would still get my length and the width that i want.