I made a topic along time ago when I had the same problem and someone uploaded a video of cybrax doing the trick, I checked that topic again but the video died and I do not have it :/
but just follow what these guys told you the best you can, I have done the trick twice ever in my life, but each time I had no idea where to fall and ended up back on the legit route after falling through the building for a few secs. and everybody knows how much I played CE, (bout 986 combined plays on M1/2/3/5!) so in other words, goodluck getting it pulled off in a run.
I would say 1:21 is possible(maxed most likely) descending and ascending though, so there is plenty of improvement left for you if you cannot do it. you should not feel bad if you fail to do it though, cause it is only the hardest and best record on the whole site :P