A tailwheel that is free castoring will add considerably to directional instability during takeoff and/or landing. In other words you will making it much harder to control.

If you wish to have a tailwheel that is not steerable with rudder then drip CA in the tailwheel block and make the wheel fixed straight ahead. This will work very well.

Did you know that many full scale heavy taildraggers such as DC-3 and others had tailwheel locks that locked their steerable tailwheels straight ahead for takeoff? Even the Cessna 185 series offered the option of a tailwheel lock.

John[8D]