What to do with that rubbish bag.
When we go to the real places we take all our rubbish out with us. When we plan and pack our vehicles, we do not give it much thought. You do not want it inside the vehicle anyway. So this lands up on the roof rack. But nowadays we have an RTT and solar panels there. All that backup space gone. Here is a nice solution that straps on, when doing trips where it is needed. 
It fits any spare wheel, from huge down to a Jimny. (That is why the straps are so long. You can trim them to your requirement.)
The profile is pretty low and will not steal much of your rearview. If that is a concern you can strap a collapsable crate to it and only erect it when needed.
You can handle a range of needs like just a milk crate to take the rubbish bag and maybe the wood you buy along the road.
It can also be the cooler box, bait box or fish box on that Henties trip.
That strap up to the box handle is adjustable to get rid of the flapping tails.
The two ratchet straps used for strapping to the tyre have a spacer/gripper so it will not slip off the crown of the tyre.
You can even bolt your Jerry can holder on top of the frame. No problems anymore with those high up on the roof items that you cannot reach and that catches on low roofs and branches and creates wind resistance.
And for the weight watchers, it weighs in at a mere 2kg.
Those with the sharp eyes will notice that two of the Jerry cans are not.
Those are boxes that fit in the same space as a Jerry can. There are two different configurations. One is a portrait and the other is a landscape configuration.
The portrait configuration has a hole in the top for your braai grid handle. Both have the option of a shelf/tray. (Please note, these are not weatherproof.) The boxes are built on request