Hey Tony
What are you planning on towing it with??
SA Law dictates that the combined mass of trailer and load not exceed 75% of the towing vehicle. So this would mean that at approximately 2 tonne for a trailer and 4 tonne for the carrier, the towing vehicle must be at least 8 tonne ( that's like a laiden Aaco ).
And that any trailer with a curb mass greater than 2 tonnes have trailer brakes ( of greater capabitily than over-run braking ) and break-away locking brakes.
I don't know if the flaws ( oops Laws ) are the same in NSW, but that pretty much dictates what you can tow a carrier with.
As far as "doing a Brocky" ( fishtailing
) down the road, most electric and air braking systems have trailer brake controls so that you can slightly apply the brakes to prevent this from happening on braking.
Pedr
Picture is Alan Newton's carrier on MVCSSA's trailer.