you only put the feed dog down if using the darning foot for free motion, when using a regular foot you need your feeddogs functioning, this helps move the fabric...you also keep them up with a walking foot, the walking foot keeps the top and bottom moving equally, if the feeddogs are down/ or covered, this does not allow this vital function to happen. i quilt on my machine with different feet all the time...but the feeddogs are a vital part of the process unless you are using the darning foot (which is round and does not hold the fabric down)and practice. you do need to put needle down before raising the pressure foot when turning but curves should be easy enough just going along, as long as your feeddogs are helping you along