Hollo I'm pretty sure they're still just guidelines rather than law. It goes on the Australian standards and the manufacturers recomendations.
THe Qld regs are harder to navigate from NSWs where I can tell you definitively. There was a push to update the Australian Road Rules (national) but they only got as far as putting in stuff like no child restraints/children in the front seat where there is an airbag etc. The terminology they used is 'approved child restrain', which means Australian Safety Standards.
This is from Q'ld Transport
Child car seats
Once your child outgrows the infant restraint , they can start using a child car seat. These restraints are suitable until the child reaches 18 kg (about four years of age).
Some manufacturers sell child restraints that can be converted to differerent types—for example, lying down or sitting upright. With this type of restraint, the manufacturer may specify different weight ranges (for the child) for the different types of use. A child restraint should never be used outside the range specified by the manufacturer for its type.

Child car seats can only be used on forward-facing seats. They are attached by an anchor bolt, a tether strap and the car's seat belt.

Child harness
A child harness is designed to be used with a lap seat belt or a lap-sash seatbelt to provide extra safety and protection for the child.

If used with a booster seat, a child harness is suitable for a child weighing between 14 kg and 26 kg.

If used without a booster seat, a child harness is suitable for a child weighing between 14 kg and 32 kg.

The manufacturer's instructions should be followed when a child harness is being fitted. When using a harness, you must adjust the seatbelt first so it fits firmly over the child's hips, then tighten the shoulder straps, making sure they are not twisted, and adjust the tether strap.


Don't know if that helped or not.
From personal experience, I've been to way too many crashes where kids were not restrained properly, either by slipping out under the belt or the sash hurting thier necks because they aren't big enough to fit the belt properly.
At least make sure your booster has a neck restraint for the belt so it fits her properly and an anti-submarining clip for the lap part.
We have a maxirider too. It is much more exie than the Hipod, but the hipod seems to be taller???
In NSW they reccomned that children are in a harnessed seat until they're at least 140cm (from my baby brained memory...).

Sorry that was long wasn't it....hope it helped a bit.