This was a pretty tough segment, and I still made some small mistakes, but it's yet the best outcome out of a huge deal of tries, so I didn't bother redoing it.
Performing an airwalk from the doppelganger room to the switch that opens the final door, happened to be about 1-1.5 seconds faster than the 'regular' route (using a left roll to get on the upper level of the doppelganger room and proceeding the intended way from there). Also, it was much more reliable of course.
Dealing with the Torso without wasting too many shotgun shells and a too great amount of time simultaneously, appeared to be doable very comfortably.
Later on, in the pool area I happened to mess up a couple of things, most notably the final swandive not directly leading into the water, but well, after all it was not that much of a timewaste either. :P