I think for WA conditions the tectonics Falcon F1 would be the go. ChrisL and Claude use these to great effect in the chop on the Swan. 2ndWind sells them (~$300 I think) but it is a fairly simple and quick process to get them direct from Tectonics (see their web site) and with the strong Aussie $ can be landed for about $220 (ask Snides or 25)
Chris' own fins, while fantastic for Sandy Point, probably would be too small for WA (max size 23cm). Mal's 26 probably falls into the same category but you may get away with a 26 depending on your size. Though these are really specialized for the 40plus speeds of SP (low cav designs) and are ~$400.
Steve at Windforce has some Meanline fins in the size you're after. I think they are about $225 and are made by legendary shaper Bernie Brandstaetter and used by BjornD. Some think they are even faster than F1s in certain conditions. see Frank's comment at the bottom here
www.gps-speedsurfing.com/default.aspx?mnu=forum&forum=1&val=3894