Our company recommends a similar test set-up to testing to IEC61000-4-4.  The reference grand plane shall be used.  The EUT and cables are insulated by using a 0.1m support from the ground plane.  The distance between the simulator and EUT shall be 0.5m. 

If the supply cable of the EUT is of a non-detachable type and is longer than  0.5m, the excess length of this cable shall be folded to avoid a flat coil (non-inductively).