Quilts have a way of moving around on the frame! As you quilt, it causes certain areas to be drawn up, depending on the density of the quilting. One way to avoid this is to measure from the center of the quilt to the edges every time you roll the quilt on the frame...if the quilt is 90" wide, you want each side to measure 45" from the center, pin it and quilt the edge of the quilt down in a ~ pattern (this allows you to suck up a little extra fabric if you need to without getting a tuck). I measure and pin about every 6", then baste it down so I can keep the quilt square. I know that by the time I get to the bottom border, it always has a bit of "fluff" because the rest of the quilt is quilted and has shrunk up just enough to make the bottom border a challenge.