I didn't know about measuring the middle when I first started quilting, but at that time my quilts were hand pieced and hand quilted. However, my first exposure to a wavy border was when I added a border to a Drunkard's Path that my grandmother had pieced years before. I could never figure out WHY there was sooo much more fabric in my borders. I didn't "get" the stretch involved in bias pieces. Experience is a great teacher. Since then I measure the center and then ease on the borders. Always works better! Good luck!