For the Dominator; I do not know!
For most Gyros the answer is, "There is No clearance at all."
https://www.youtube.com/watch?v=DJ4EpCphp18
With the Cyclic fully back and the Rotor at the Teeter Stop limits, The rotor WILL strike the tail.
This is what is mistakenly called "Rotor Flapping". In helicopters, it is called "Mast Bumping."
In gyros, It is really "Teeter Stop Bumping" and has nothing to do with anything "Flapping" other than the flapping caused by the bumping.
Rotor Blades do not "Flap" because the Rotor Speed is too low. They Flap because the Teeter Stops are being Bumped.
Under normal flight aerodynamics, it will not occur.
The problem is when the Rotor Speed is not sufficient to absorb the excessive incoming airflow.
The Right Advancing Blade climbs in the higher airflow and the Left Retreating Blade descends in the lower airflow.
This causes the roll to the left that Juan de la Cierva cured with the invention of the Teetering hinge.
The initial assumption would be that the rotor disk would tilt to left. Not so.
The Advancing blade reaches its highest point in the front and then become the retreating blade and begins descending.
This is why the Rotor tilts Backwards.
The Teeter Stop Bumping commonly happens in the takeoff phase with low rotor speed and high ground speed.
Pre-Spinning the Rotor up to sufficient RPM before the takeoff roll will limit the amount of teetering and prevent Rotor Strike.
It also can occur in normal flight with normal rotor speed coupled with high airspeed.
The faster you go, the further the rotor disk teeters backward.
At some speed, the rotor will start bumping the teeter stops.
This is what determines the Vne (Never Exceed) Airspeed of the Gyro.
It would not surprise me at all that the Dominator Rotor is capable of striking the top of the Rudder.
It's what they do!
It is also why Rotor Speed management is important.