My last session at Burrum I found I was fighting Wind, tide and waves just to maintain ground.

Assuming full planing conditions, what specific changes to rigging can be made to aid upwind ability?

There seem to be so many tuning variables involved, can someone give me the magic formula?

As Mineral said, lean forward, rake sail back.

Tuning tips:
More outhaul (flatter sail), bigger fin.

Thanks nebbie, commiserations about the break in.
What about harness line position, does a little further forward help?
And mast foot position?

i'd have to say more outhaul to tighten up the leach, in the surf you can ride waves upwind and tack off before they close out, them you can gain heaps of hight fast, then bear away on the big ones.

I think in most cases a big flat sail, (not necessarily, just outhaul give it enough downhaul as well)
will have it's center of effort further forward than a bagged out small sail, who's center of effort will be further back in the sail, giving more sideways drag, overpowering the fin.
The other thing to watch out for is oversheeting, that's part of the effect of leaning forward, not only does it help to get more rail in the water, it also lets the sail sheet out a little.
I'm not convinced about engaging the windward rail, that make the board want to turn upwind sure, but it's not a good trim position, adds more drag, forces you to lean the sail forward, killing some speed.
I prefer to engage the leeward rail, although that makes the board want to go downwind a bit, raking the sail back further counteracts that, doesn't affect the trim and speed as much.

I had a boom failure yesterday, the arm adjustment slipped on one side, had a very surprising affect, the sail really bagged out on the starboard tack, but was almost normal on port, the difference in ability to get upwind was very pronounced, just didn't want to happen on starboard.