The mount is really stable and seems completely unimpressed by the 6kg of my 32". The specified payload is 8kg. I assume that the 8.1kg of your screen should not be a problem.

Hi,
My monitor is only 24" and certainly weighs much less.
The approved size is 43" (or 49" ultrawide).
Max. Max. load is 8 kg, but you can certainly tighten the screw connections of the various joints a little more so that the monitor doesn't fall on your feet straight away.
However, the VESA mounting only allows 100 x 100 mm!