Quilter's Dream Select is a very light cotton batting in keeping with your natural wool. It would not add much weight but does not pull apart when handled. Their Request thickness is mainly for hand quilting. Also consider a very short stitch length and pressing seams open with steam. I have started pressing most of my seams open. With the very short stitch length I have had no problems. I know some feel this is sacrilege but it works for me. You may need to lighten your the Presser foot pressure on your machine. Also consider stitching with a walking foot. I have differential feed on my Bernina 880 and use it all the time. I also love piecing with a featherweight and plan to try a walking foot with it on cotton at a retreat the end of the month as I am piecing with 16" squares.
