Over 0.5 FHG
This post shows how to create the rule
viewtopic.php?f=47&t=11621
Or you could use this ready-made one and just adjust the odds to what you want
viewtopic.php?f=52&t=11414
viewtopic.php?f=47&t=11621
Or you could use this ready-made one and just adjust the odds to what you want
viewtopic.php?f=52&t=11414