Note that the description is wrong. It's not a maximum of 20 lbs, it's just that the counterbalance is weighted for 20lbs. If you have 20 lbs worth of tabletop on top of it, there's basically no effort required to lift the table. I'm not sure what the maximum would be, but I was not concerned about my 45 pound monitor at all.
It got replaced with a "real" standing desk when we moved.
Basically all I did was screw a couple of boards to the top of the frame, and then C-clamped the bottom of the frame to a desk. I was always planning on doing it "properly", but never got around to it.
Note that the description is wrong. It's not a maximum of 20 lbs, it's just that the counterbalance is weighted for 20lbs. If you have 20 lbs worth of tabletop on top of it, there's basically no effort required to lift the table. I'm not sure what the maximum would be, but I was not concerned about my 45 pound monitor at all.