Hi 19MisterJay89, I have 2x 29" BenQ monitors weighing 9kg each on the Ergotron LX in use. It works flawlessly and the adjustment options are many and the whole system is very stable. Ergotron states the load capacity per arm as 9.1kg. (https://media.ergotron.com/reserved...).

Bear in mind that the compression springs that hold the weight of the monitor would eventually reach their limits and no longer be able to hold the monitor in its desired position. I feel I still have 2.3kg in reserve, but since your monitor weighs 16kg, I would be critical. It's best to ask Ergotron directly.

Keep in mind that the width of 43" limits the movement radius of the second monitor. I also recommend trying out the stacking of 2 monitors on top of each other first, the vertical tilt of the head can be very uncomfortable. I decided on a variant where the main monitor is directly in front of me, and the 2nd monitor to the right of me at about a 45° angle. Also check out the video "Dual Monitor Productivity Setup Guide 2022" on YouTube, (https://www.youtube.com/watch) which I found extremely useful. I hope it helps you.

Addendum: No, not every movement has to be fixed manually. The compression springs create resistance and hold the weight of the monitor in position. The system is therefore fluid and you can rotate / tilt the monitors "in real time" to any desired position.