The Multifunction Arm system is fantastic, but, being made from plastic, not 100% rigid.

Gravity, on the other hand, is a bitch, and won't hesitate to flex and bend the system until your screen or other device on the end of the arm is not exactly straight anymore. Fortunately, by placing one of these shims in your setup, you can compensate for the sag and get your devices to hang straight. 

The shims are meant to go in between the parts that are screwed together (see photos).

For an accurate shape, use low or variable layer height with ≤0.15mm at the top.

F3D and .step files included.