I use Monopoly in my Bernina 820 for ditch stitching quite often. i always use Superior #100 Microquilter poly thread in the bobbin. It works much smoother than using Monopoly in the bobbin too. Microquilter comes in 30 colors so along with it being very fine and sinking into the fabric, so it blends in pretty good. It is also strong and doesn't break easily, the Bernina likes it.
I leave the bobbin tension as is and set the top about one half or less, a little test sewing will help determine correct setting.
This is the best combo I have found.