The Airhook was designed with the person reclining in front of you in mind. Thus, the adjustment knob was added to the design to add for enough compensation to be able to bring the liquid [in your cup] back to level. The device angle moves slightly, but not at the same rate as your cup.
After additional testing post the Kickstarter video, we decided to make The Airhook slightly longer in the rear. This will allow your device to sit further away from the seat in-front of you and will provide greater viewing adjustability.
Please stay tuned for additional videos to help show the elongated version and adjustment capabilities.