The idea that the size of the vertical fin somehow slows the yaw rate in a hover is flawed to start with. Then to make a fancy contraption to reduce this non=loss is folly, then to make another contraption to fix the poor yaw handling at cruise is further folly.
Why not look at the initial problem that you think exists - remove the vertical fin, run the tail rotor as is and measure the "improvement" in hover performance and yaw rate. Report the findings here, and prevent Dave from spending all those billions of electrons here in pprune fixing fictional problems!
At a yaw rate of 30 degrees per second, a vertical fin on an S76 has a velocity of 13 feet per second. Its drag coefficient at 90 degrees is probably 1.3, so it resists the yaw with a grand force of about 8 1/2 pounds. To chase this 8 1/2 pounds (at a 30 degree per second hover!) Dave would redesign the whole ass end of the machine!