well as if that video does not tell ya! haha i can let you know i have both a 55gal and 75gal all glass aquariums that i placed a sheet of 3/4 styro foam on the bottom layer and then placed about 150lbs of rock in the 75 gal. and a good 200-250lbs in the 55. They are both holding strong!

The main idea when putt rock on glass is that you want to distribute the pressure over as large of an area as you can. If you focus it all into a small 1cm squared area because the pointy part of a rock is pressing directly on the glass its probably going to break with no issue at all. Add something to relive any pressure points like that and distribute it over a large area and you will be fine.