[Therion] Offset legs in diving data

I have some diving data, in the form data diving from fromdepth to todepth compass tape LRUD data has also been collected for these sumps. I would like to be able to display the latter as offset legs in the th2 file to aid in drawing the map. How does it need to be entered into a th file and how do I then generate a background for th2, as is down with DistoX data? Graham