The machine does not know what size frame you are using when you use Fast Frames. The machine arms that hold the Fast Frame are extended to the largest size hoop so that is what the machine 'sees'. It is wise to always do a trace when using non-standard frames so that you know your embroidery will fit inside the area available. I have hit the metal FF even after I traced a design so I always make certain there is plenty of room for the embroidery foot to clear the edge of the frame.

Basically, the machine thinks you are using the largest standard hoop which is, I believe, 300x180 when you have the FF on the machine.

I am thinking about buying the fast frames so much more economical. I have an mb4. Are you happy with the fast frame? Or should I wait and purchase the quick snap