In my memory (which has a few gaps in it - Broome has a good nightlife) I don't think the wind has ever gone over 20kts (except with the cyclones), I don't think you'll need the 9. Unless you're 40kg or less. The Bureau readings up there are pretty accurate,
www.bom.gov.au/products/IDW65029/IDW65029.94203.shtml , and in my experience the best time for kiting there is October/November and a couple of weeks either side, so not quite yet, but don't take my word for it.