With the help of my trusty catpanion, I replaced my old VIVO arms that were precariously near their weight limit (within .23kg), with a new set of AVLT arms, rated at 15kg (33lbs). The iMacPro is 9.75kg (21.5lbs), so well within the range.
The old arms were fine for lighter displays.
As can be seen, the AVLT are really sturdy. The slip-in lock thing makes it easy to wrestle the iMac into place and slide it onto the arm.
I still have some cable management to do (the troughs are currently removed).
The arms will also go as high as I want, but are about 5cm (2") shy of letting me vertically stack the iMac/monitor. With two 27" displays, this would probably work.
Before installing the VESA mount. Kind of precarious, and not quite high enough.
Nice setup Congratulations, I got myself Ergotron arms, they are just amazing and sturdy. I tried my luck with Jarvis, but it was vibrating with my keystrokes even the Fully pole keeps sliding and the monitor loses the height. This is why I mentioned previously, arms are very expensive, not something to try and replace, the process is more expensive.