i'd go one size down and an 8m, don't want to be sitting on the beach when its nuking!

yo , depends on weight and what you ride ,i live in the middle of wa generally the winds are a bit stronger here, i have an 8,9 11 17 quiver, the 8 was used once last summer the 9 maybe 10 times with the 11 being used the most , i had the 17 out heaps aswell, i weigh 90kgs and ride a 135 twinny, however i reckon this year looking at the winter weather graphs its gonna be a bit stronger, if your on a twinny and have a bit of weight to you the 9 will be fine, the rallys have plenty of depower from what ive read, enjoy your time in wa