Go with 0 to start. If you notice a tail control oscillation that can't be corrected with gain adjustment then you may need to go to a higher delay setting. On that setup, though, it should not be needed. Typically only used if you're using a slow servo or it is a large heli with under performing tail setup (smaller than ideal blades, blades with a lot of flex, poor mechanical setup resulting in sluggish rudder controls, etc.).