I have a Bernina machine but as well a Husqvarna Viking RUBY embroidery machine, I have a Fab-u-motion with the stitch regulator. The stitch regulator of the fab-u-motion is not efficient at all, I do not like it BUT I like very much the Fab-u-motion, it helps a lot for the free motion quilting, we do not move the quilt but only the frame of the fab-u-motion under the quilt, the quilt is moving very very easly under the needle of the machine, without any effort, It is very difficult to explain how it works but I have quilted a very large quilt 2,50 m x 2,50 m,1 m = 39inches.(go on Youtube - Fab-U-motion) You can use this Fab-u-motion only on Husqvarna Viking and Pfaff machines, and not on all type of Viking and Pfaff machines I suppose. The height of the arm of the machine is very important, I cannot use it on my Bernina, the arm is too high. I hope it helps.
Chantal