Our Tail Rotor Enhancement Kit for the UH-1H series uses a single BLR strake on the tail boom. There is definitely an increase in authority over not having one, but the main difference is a reduction in pilot work load in crosswind hover. By spoiling the airflow over the left side of the tail boom the pedal excursions are reduced. In a cross wind from the left front quarter there is usually a pedal reversal required to keep the aircraft straight at about 10 knots of wind speed. The strake reduces that effect. I have also tested strakes on Bell 206B and L and found the effects to be pretty small, likely because the cross section shape of the tail boom is small and circular in shape.
The EH101 has a big single strake. NASA did a strake test on a Bell 204B and I think the test report is available, if your interested.