If we were you, we would quit now.
Quote from Lazylen:
cool. how do you do it? just jamming space? I wasn't able to do any infected acrobatics near release, but maybe that's changed (one spot I could get to was above the subway entrance in NM1)
Find a spot you want to get up to. Stand on something that is slightly higher than the zombies. Thats about it. Also, to get zombies to a certain point, use a pipe bomb. Then, just jump off the crowd.
Examples:
http://rapidshare.com/files/200240534/dt2_eventskip3.dem.html
http://rapidshare.com/files/200240683/dt3_endskip.dem.html