Belt installation details:

1) Slide belt through tail boom.
2) Install tail rotor assembly onto the boom.
3) Verify that the belt is not twisted inside the boom by pulling on one side of it.
4) The rotor should spin in a counter-clockwise direction when you look at it from the side that has the blades on it. To achieve this, hold the tail boom with the blades facing the floor. Grab the belt and then rotate the boom into its proper installation position (vertically). The belt should now be twisted in the proper direction.
5) Install the tail boom into the frame and make sure the belt is installed in the orientation that you achieved in step 4.
6) Test by rotating the main rotor clockwise. The tail rotor should spin CCW or up into the main rotor wash.

Servo placement is determined by the helicopter behavior. Start by setting the rear pitch fork in the middle of its travel and positioning the servo on the tail boom so that its in its neutral (zero) position. Tweak as necessary for proper tail control.