I have a Janome 4800 as well and I have used some of the decorative stitches for quilting. I have to be very careful and let the feed dogs feed the quilt, the least bit of pulling will result in skipped stitches and different lengths between designs. You can't enlarge the design but you can lengthen or shorten it. I haven't done it in a while but if I recall correctly I get better results with a walking foot.