I recently took a workshop with Rita Fishel at Shipshewana, she uses her FW for FMQ; she has a generic low shank darning foot, leaves the feed dogs up, turns the stitch length to "0" , adjusts the top tension by using that little metal button on the top of the machine (sorry don't know it's name), I haven't tried it yet, but it sure was working well on her sample. It was only about 12" square and she says she doesn't use it for anything larger than a baby quilt. I think this is the shop she's from, at least they have some of her patterns.
http://www.creationssewclever.com/