|I haven't tried this but have the info from an old Bernina list I was on. Someone asked about how to do it and I hope this helps. There are three different methods.
For all - Use a walking foot with monofilament on top and 50 wt cotton in bobbin (Or Mettler silk finish or Sulky rayon 40 wt in bobbin). Play with the tension a bit.
1. Stitch #5, length 3-4, width 0, balance -8, tension 7-8
2. Stitch #14, length 5, width 0, engage long stitch function, balance -20, tension 6
3. Stitch #16, length 4, width 0, balance 2, tension 7