I have fished both ends of Dirk Hartog and Steep Point a fair few times and have not seen a GT. We have come across schools of small goldens but that is about it on the trevs. I have heard rumours that the islands to the north do hold GT's. Throwing stick baits and poppers along the drop off they call the Fault Line will produce big yellow fin and macks. Some of the yellowfin are trains!