Hey Mate, found several useful 5.8 tuning guides from these folks. Right in your back yard (I think?).

http://goosemarine.com.au/Articles%20|%20Photos

Mine is a 5.5 Uni so, for what it's worth,upwind mid-point on the traveler track to begin with and then adjust according to wind velocity.

Downwind, let her loose and travel out all the way.

Sail fast, Tom G