While I like a bit of Expo on the rudder, I find that it is best to keep the rudder Expo setting somewhat LOW for the tail wheel.

Expo tends to deaden movement around stick center.

When the plane is in the air, Expo on the tail is great, but the problems lie with the takeoff.

During runup the plane will yaw, and you correct with a bit of rudder... however nothing happens because of the Expo.

You correct again, and you do not obtain the result your brain thinks you should get... so you correct again.

By this point you're slamming the sticks and have the plane jinxing back and forth as the Expo causes more movement at the extremes.

I find that 15% rudder expo with full deflection is what I need on the ground.

In the air I keep the same deflections but I may turn the Expo up much higher... in other words my dual rate switch only changes Expo for the rudder.