The RSX is often more associated with active Raceboard classes.
Raceboards are sailed a lot at Dobroyd point
www.dobroydsailing.org/home/You will get a lot of info at
www.lbws.com.au/ about events.
The Aussie RSX class can be found at
www.rsx.yachting.org.au/formula Boards race regularly around Sydney (www.storm-riders.com.au) - the RSX is not a great fit with Formula boards, but there are always some out on summer weekends if you want to practice.
JB