dunno where else it should go but this is about 2 points in E1 at which we wait for an event to complete. that being the nerve-end elevator and cult stoney room. simple strategy I found is to wait:

• 32 seconds after triggering the elevator, at that point the invisible wall will disappear at a perfect time to make the long jump to the end.

~55-58 seconds from pressing the lever in the stoney room, at that point the final enemy should begin to move. allowing you to kill them all at once before spider popes become a problem.