I didn't have the greatest of luck with the triple mount monitor arms either. The tolerances just aren't there. There's slop between the sleeve and the hinge, then slop between the sleeve and the mounting bracket. Mine were done correctly as far as the symmetrical spacing but there's still enough play to have an appreciable drop by the time you're at the end of the arm. The joints just aren't well engineered. If I get motivated I might go turn some bushings to clean up the sleeve's fit but for now like I mentioned above I compensated by using that lower hole on the monitor mount assembly.
