All of them that I have seen, to include mine have a set of "centrifugally operated flap limiters" mounted into the tower. If you are parked and the blades are stationary, the limiters will be in their lowest position. The limiter in relation to the front should keep the hub bar from pivoting far enough to allow the blade from hitting the tail.
manually, rotate this out of position and the blade can flap far enough to touch the tail.
While, taxing or stopped allowing the blades to slow down, depending on which direction the airflow is coming from. Between 45 and 80 RRPM.
really, anything below 100 RRPM. The limiters assist you to keep from having a blade strike into the tail. On mine it will scare the crap out of me. I have to use both hands to hold the stick and it feels like the gyro will turn over. and the stick is full forward and rotor brake engaged.This depends on the wind speed and direction that it is feeding the disk. The best case scenario is the let the wind come from the right side and rear quadrant (4 to 5 O'clock position) If the stick was pulled to the rear, the blade would most likely hit the tail.
In the first picture, you can see one of the "I" shaped limiters I spoke about.