Tosh: good eye, indeed, it's a 5.7 I used at L'anse vata but a 5.2 on the reef.
It was not my own gear but I've already been there with my formula gear (actually a RS:X 9m²). Most on the time in the lagoon, it's pretty flat or a bit chopy. Your option with the 7.4, 6 and 5.4 looks like the best as in september, you can get between 15 and 25 knots from south east... or nothing at all.
Ray: don't talk about uni to hannah or she'll never come back to Brisbane ;-)
By the way, I have to tell the Hannah's strategy when she sails on her home spot:
beach start, straight to the "ilôt canard" (island you can see on the pics). Then get off the board, turn it and go back to the beach. No jibe or tack! Too easy!