If the current is crap down off SE QLD, I have noticed the GT's will happily follow any school of small tunas in the vicinity.
It's cool to watch a GT boof a 3kg mack tuna off the top.......they really move some water around doing it!
This is the "oh crap, there is no current and no other small baitfish" alternative. It is a long shot when all else fails.
I'd say Brett, that like several others have mentioned: find any current and the larger GT's will be there.
Some very fired up looking black ones in amongst the captures!
Cheers,
Aaron.