I just found the youtube video with the big foot before I notice you reply. Is there something odd going on with your machine like fitting screw problem? The basic foot is working fine? Yes, the low shank is the most common standard for the old Singer straight stitchers, lots of others too. What complicates it is that the distance between presser bar and needle clamp movements aren't the same for all models. A silly mistake, but very common with darning and free motion is to forget to lower the presser foot before we start to sew. Usually you will just get tension problems, but it will mess up the needle clamp distance for the jumping foot.