I guess i was born with crooked genes because no mater how hard i try i can't sew a striat line. Most of my quilting is s stitch in the ditch. So i bought a sitd sewing foot. i run the blade right down the the seam. But im still off track. it runs about a 1/16thto 1/8th off the ditch. do you set the foot some how ? what am i doing wrong . why wont my ding dang darn stitches stay in the ditch?