I cut using the first seam line as my guide. I don't cut to the middle of the nine patch exactly. If my finished center block is suppose to be 5 inches, I cut from one side 2 1/4 inches and from the other side 2 1/4 inches. I have a little strip left in the center of about 1/2 inch. But all of mine are then the same size. It has to do with the turn of the fabric in the seam allowance.