I have a Janome 6600P, and I have the dual feed foot. I also have what I thought is a stitch in the ditch foot. It looks just like the dual feed foot, but it has the piece of metal under it that I think is supposed to ride on the seam. However, if I put it onto the seam, then the needle hits far away from the ditch. What am I not understanding? Does anyone else have a SITD foot?