We keep our second spare on the roof. 

Factor in the loss of payload with a draw system. People pull them out for this reason.

You will probably have to do a custom built to get it to work to your requirements. It takes time & it's good to get off the project as this is usually when problems are solved. I have built a number of complete custom items for my car. Including a fridge mounting bracket as the standard one would not work in our limited space.

My 3rd row of seats in my GQ Patrol have been sitting in my shed for over 20 years .. since I purchased the beast.  

When I go Van touring I remove the second row as well.

From time to time I hear that it may be illegal to do so, so I did a bit of a search and found an article in Outback travel

    4WD Modification Legalities (outbacktravelaustralia.com.au)

 and took this relevant extract.

Draw your own conclusions.

In my case, I reckon that I am legal in that the temporary removal of each seat requires the removal of 4 bolts with a simple tool (spanner) & the seats can be replaced as required.

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Seat Removal

Many 4WD owners buy wagons or utes that have seating capacities from five to eight persons, with the aim of removing the rear seats and using the rear seat space for travel and camping gear. There is some uncertainty in the 4WD community about the legality of such conversions, so we sought responses
from some State road transport authorities.

Transport South Australias view is that removing rear seats, where no tools or only simple tools are needed; where no structural modifications are involved; no change in vehicle category and no commercial gain is sought; does not need approval and so is not committing an offence.

Providing no anchorages for seat, seat belt or child restraint are removed or modified, no modification has been made to the seating capacity. However, if the seat cannot be returned to its original position because of the removal of an anchorage point, then a permanent change in seating capacity has occurred. To formalise this change in seating capacity, an inspection will be required and following inspection a certificate of exemption issued for the permanent removal of the seat.

Where the seats are removed to change a vehicle registration category; to skirt established arrangements such as ADR certification; or to make a substantial structural change relevant authority approval is needed. If any change in classification is sought, an inspection is required and a label attached
accordingly.

Vic Roads view is that there is no reason seats that are designed to be removable cannot be removed. Doing this does not alter the seating capacity of the vehicle. Seating capacity is defined by the Australian Design Rules as the maximum number of seating positions for which the vehicle is designed; not the number of seats actually fitted at any point in time.

The NSW RTAs position is similar to Victorias in that rear seats may be temporarily removed without affecting the vehicles compliance.

Queensland Transport says that for vehicles fitted with quick-release seating attachments as original equipment, temporary removal of the seats is acceptable.

In the case of vehicles fitted with bolt-in seats no engineering approval is necessary for temporary removal, provided the category of the vehicle does not change as a result of the seating reduction.

At the time of a Safety Certificate inspection, the vehicle must be returned to the manufacturers original condition or have a Modification Plate fitted for the seating configuration as presented.

Queensland Transport will mutually recognise interstate drivers travelling in Queensland who comply with their own jurisdictions requirements, but drivers are advised to carry some proof of this compliance.

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