I bought this from Amazon for my 65″ Sony. I could happily sit on it at full extension. Well, not happily because it wasn’t very comfy but it was solid!
Could have easily spent £300 on something similar but I just don’t see the point.
That’s mounted to blockwork with Rawl bolts. The expanding metal type ones.
The one I have upstairs for a 40″ Samsung was about £9 delivered from Amazon. Hung on plasterboard using toggle clamps and it’s absolutely fine. Not sure I’d want to sit on that one though.
If I was hanging a heavy TV on a pull out mount to plasterboard, I’d bite the bullet and remove the plasterboard to install some studs/ noggins in the right place.