If I could go back in time and advise myself about what initial wave board to get with the knowledge I have now for a 80 kgs I would say get a 90 to 95 litre board with a fast wave rocker line about 56 to 57cm wide with a tail width of about 35 to 36 cm get a big 25 cm deep wave fin. Use it for about 2 years then get a board with more rocker and a bit less volume. A big board will be more forgiving, give you more time on the water and speed up your learning curve.
The penalty of going to big is it would feel bouncy when it gets really windy..... BIG DEAL !!! I have seen some exellent wave sailors that have learn't how to use big boards and in doing so get going earlier, get more jumps, get upwind higher on the wave than others. If useing a too big a board on mast high waves say at Margs then you won't be able to muscle your way with it. But for waves around Perth it won't matter.
See Mattress Busters comments in the comparing volume thread.
I hate talking about boards in volume and litres cause you can have 2 85 litre boards one may be 54 cm wide with lots of rocker and would be a pig to get on the plane yet the other one could be 58cm wide and get on the plane really early. See Hardmans comments in light wind options post re width

Yeah bluejuice is right.

all that advice is very helpful, thanks.

but I wonder what board bmanners is using on the river?

I probably spent a couple of seasons at point danger, Torquay on slalom/freeride gear before getting a wave board and my wife, who is just in harness and straps gets out in the waves on her Fanatic eray 150.

I'm 90kg and use a fanatic PM87 goya and have no problems. But being no expert wave sailor I probably don't know enough to realise I'm not having the fun i think I'm having.

best winds

brett,
all the pics seem to say better waves over there.
I'm 2hrs drive from torquay in central vic and so have to sail lakes a lot and do so on a Sonic australia 275 freeride and KA koncept 6.6m. Mainly gusty conditions. when things boost in the wind stakes and I need to go 5.3 or less then out comes the goya and it is serious fun in the chop, stays under control ( the sonic goes ballistic) and lets me practice some more adventurous stuff.

5.8m is the biggest sail i'd bother with on the goya so at torquay

the choice is simple 5.8m + then freeride 5.3m or less then the power is ample for me on the goya.

so I reckon that you should go wave sailing on your rrd and when you get keen on more powered conditions try a couple of demos.

I used a RRD 66 freeride at Hookipa and had a ball. didn't look to proffesional but who cares.

best winds