I knew someone who did something sorta like that from the Sepulveda overpass.
This is the actual piece he did in 1997, I assume the picture is that old as well... Believe it or not, thats an 80-100 foot tall pylon he was on.Then he fell(jumped) and broke his spine, both ankles, and his arm I think. Doctors said he wouldn't ever walk again, but I think he was walking again by 2005.