yeh this is very hard and takes alot of patience
you have to walk until you hit the edge then crouch
turn 45degrees to the line and walk a bit left and crouch ,,,
if you can stand then walk abit left and crouch ,,, crouch again .. if u can stand keep repeating the process until you cant stand under the ledge...now aim to the straight line infront of you
from the straight line turn a little say 10degrees to the right and very slowly walk to the left/right and try to crouch if you can stand up your likely to do the elevator if not repeat it all over again