I had to go a little higher than the 5.1nm torque spec on my X2. The face plate bolts would back out and come loose.
My torque wrench has 2nm increments. When set half way between 4nm and 6nm the face plate bolts would back out over time and eventually loosen up. Greased the bolts and inside threads, increased the setting on the torque wrench little by little and they seem to stay put at about 6nm.
-Tim-