I'm running a schumacher mi2-ec so probably won't be much help on car setup. I run a Futaba S9402 servo. For the gtb/4.5 combo at brendale I would start with gearing around 9.5 or 9.8:1 and adjust either way from there.
If not before, then early in July there is a "winter championships" at brendale which will function as a kind of a warm-up for the nats. I'll probably/possibly run at that event and can let you know how the 4.5/gtb combo works out + gear ratios etc. All our setup info etc (including brendale) is on our website
Entry forms won't be out for a while yet. Keep an eye on this thread
in the Australian forum. That's also a good place to ask for info on the track and the event. I would expect entry forms maybe August or September.