Sailquik,
The GBR offers a myriad number of these type of speed canals. It's just their isolation and the near impossibility of all the planets aligning. Off here (Yeppoon) we have the Capricorn bunker group and a first hand experience of cruising through had me drooling in amazement at all the possible speed sailing opportunities. Of course if you don't have a seriously big tug to get you to these spots when it's blowing 30+knots you can only continue to dream. The closest to sailing nirvana would have to be Michaelmas Quay (north of Green Island) that Cam et al have sailed a handful of times.

PS - I have sailed the channel at Heron Island once in very light winds & knowing about those 3-4m+ Tigers that call it home makes for an interesting experience.