RE: shallow water
The guys have given you some pretty good things to try here.
I agree with both o2bnme and Sam that there are some better weed fin
designs that might work for you.
Here's my take on this (I just got back from Bonaire and was sailing an Isonic 122 with a 32 cm Lessacher Design with sails up to 8.5 m2 in the very shallow Lac Bay waters.) I had almost no spinout with this fin, and it cleared the bottom except when the tide was at it's lowest.
I also use a different design weed fin (Tangent Dynamics Reaper 32 cm) with up to a 7.5 m2 SW Retro and again had very little spinout.
Weed fins have quite a bit more area than more vertical fins (for a given depth or span) so you can use a smaller weed fin with a larger rig and get away with it.
The weed fins are inherently safer (in shallow waters) as well since they are raked back at 45 deg. or more and this allows the rear of your board to be pushed up over the shallow areas with a much less rapid deceleration when you get into water that's too shallow for the fin.
So, look at some different weed fin designs and see if there isn't something available there in Australia that will work for you.
The True Ames Shallow water weed series would be really good also, but I did not have one in a small enough size (44 cm is the smaller of the 2 I currently have) to work in Bonaire where the rental boards all have fins that are 32 cm or shorter. I've used the True Ames Shallow water 44 quite a bit here in Hatteras and it works well with sails up to around 9.0 m2.
The Drake 42 cm cleaver fin is pretty good, but you don't get the added safety feature of a raked back leading edge so if you "go aground" on a
"cleaver style shallow water fin, you get the same rapid decelleration (and often a major catapault type wipeout) that you would with any vertical LE fin.
True Amea makes a really nice 38 cm "cleaver style" vertical shallow water fin that you might want to look into as well.
Hope this helps,