Originally Posted by dunster

The size of the finished piece is what matters, not necessarily the size of the seam allowance. It's just that if you cut accurately and sew with a scant 1/4", the finished piece SHOULD be the right size. Instead of trying to measure the seam, try sewing together 3 fairly short strips that are 2.5" wide. Now measure. The center strip should measure 2" (because 1/4" was taken away on each side) and the outer two pieces should each measure 2.25", for a total of 6.5". If the measurement is less, try sewing with a slightly smaller seam allowance; if more, then increase your seam allowance. If you change your thread you may have to repeat this process to find your perfect spot for sewing.