Rick at WOW stretches and removes the feed dogs.
Usually when you put a machine (any size unless it started domestic) meant for a frame you loose the feed dogs. Also when you do SITD and 1/4 from seam on a frame you use a ruler and ruler foot on the machine not feed dogs.
You can get a set up with a brother, juki, or other 15-16 inch throat machine second hand if you start following some of the 'for sale' or 'quilting' groups on Yahoo!. You just need to sign up to be a member.
Good luck on your search.....