Hi Lee,
I only used 0.4m^3 (against general consensus) and had a similar setup, RC8 and NEQ6. I didn't just dig a square hole, it was a wide slab and directly over the pier i dug deeper:
http://www.iceinspace.com.au/forum/s...d.php?t=114718 (see page 2)
Never had any issues since and works fine, you really dont need a tonne of concrete (excuse the pun
) to make this work. I live in Vic and used a company called Vicmix, very cheap and they come to your door. Maybe call them and see if they have contacts in QLD?
On a side note, my mount is screwed onto a plate, and then this plate is screwed onto the pier. This way i can take my mount inside by unscrewing the plate and when i put it on next night its still polar aligned. In Melbourne where it rains and is cloudy for weeks at a time, this is really helpful in prolonging my mount's life (and not worrying at night if rain or frost is on my mount
).
Just decide a way forward and stick with it. Goodluck!