I always leave the feed dogs up, use a darning foot and don't mess with the stitch length when I quilt on my Janome 6500. I find that by doing so it enables me to have greater control of my stitch length and pattern. There is no need too set the stitch length to 0 as you determine the stitch length by the speed whith which you move the fabric. I have not found any corolation between tension and stitch length.