Greyarea,
Can't help you source the cedar around Melbourne but just so you know if you do find it but can't get the long lengths there is no problem in scarfing two lengths (>8:1) together to get the required length.
Also I underestand the slightly fuller hull shapes are doing better, however I'd be happy to be corrected by the Mossie sailors.
So make sure when you glass the keel line the resin fully cures. During our winter that means leaving it greater than 7 days before putting the hull in the deck jig.

Personally I'd also steam the hull a little if it is not specified in the plans to make sure the hull was reasonabley full. If you want to be a little more adventurous you can put a very small fillet with lightweight filler under the inner glass tapes on the apex of the keel to encourage further fullness.

If there are class templates I'd get a copy before hand to make sure I could make the hulls as full as the class regs would allow.

I'm not a Mossie sailor but I have built a lot of ply cats.
So please cross check my suggestions with the top Mossie sailors just to make sure they are relavent to the current Mossie trends.

Good luck.
If there is anything I can help with let me know.

Regards,
Phill

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!