C-2023 E1 (ATLAS)

The payload is 5.5 kg.
The only thing is the tube is long, mine is without a secondary mirror.
It handles it easily. The only issue is that due to the long tube, sometimes there's inertia and the guider can't keep up.

Here's a short lens setup: the 3M-6A 500mm + a Canon 7D camera, a guider, a mount, and everything else adds up to about 4kg. There are no issues with it; the average tracking error under good skies is 0.4–0.7.