I have SITD feet for my low shank machines, so I can do the SITD on those machines, but I'd rather do them on the frame. One thing I didn't consider though is that I may require a different presser foot for it - it has a taller "collar" so you don't go over or under the ruler. Here's a video on how rulers and SITD work on a frame. She's using a mid-arm, but the principle is the same.
http://www.youtube.com/watch?v=e2XlzHpyKSI
You're basically right, it's FMQ in that you're guiding the machine via the ruler not via the dogs.
I'm going to look at the possibility of using the extension table that comes with my machine on the carriage that handles the machine. It would save the cost of another extension. Or I may make one, but that would take time to do and take me away from the quilting.
