\df_ghost1_PlayTimescale [ DEFAULT: 1.0	RANGE: -10.0 to 10.0 STEP: float ] - sets the speed of the ghost playback.

You can change the speed of the ghost during playback.  Setting a the ghost timescale to a negative value "rewinds" the ghost.  You can rewind as far back as the ghost snapshot buffer allows (normally about 25 seconds using a recording interval of 50).