Hi there. I don't know that there is an "ideal" setting. It would vary from fabric to fabric, and backing to backing, and design to design, and of course everything changes every Tuesday... I had a problem with birdnesting occasionally until I started double-checking the thread was under the roller and in the groove correctly. I stitch on heavy denim at a setting of 6, and lighter denims at 4. Some thin cottons I do on a 1 or 2. HTH, Judy