The picture is of the new design that started with the MY10 models.
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The later hitch does indeed fit earlier models. However IIRC its rather expensive.
In this thread it was thought to be around $400.
http://www.aulro.com/afvb/d3-d4-rrs/...-hitch-d3.html
For that price it makes it a very doable option. A mitch hitch is $660 and around $150 to get it fitted and adjust the sensors and then a new tongue and ball is about another $150 - $200. Thus about $1000 all up. If the D4 hitch is under $500 and around $400 for the rapid hitch it is about the same and in my opinion more aesthetic in appearance.
Thanks to everyone who have offered help on this thread. Where I am at at the moment is that i have now arrived home after my week away and I took on board as many suggestions as I could. What I did for this trip was lowered the tyre pressure to 45 (instead of 55 as adviseed by the caravan dealership - I notice the notice on the side of the tyre says not to increase pressure above 40(I'll probably drop to 40 next trip) I thought this may increase the sway but it didnt. I also filled both water tanks and as they are both forward of the wheels it increased the ball weight. I also moved the annex towards the front of the van, increasing it more. It did tow better coming home but still had some sway on occassions. I measured the front to back of the van in access mode with the motor running and found the van to be almost 150mm lower at the front. Now tht I am home I have been able to make a minor adjustment to the HR WDH and it now fits the bar and raises it approx 80mm. I havent had a chance to tow the van since but when I have another trip I'll see if that fixes the balance of the problem. If it does I will look to the D4 fitting and a rapid hitch.
Unfortunately I am new to the forum and have not worked out how to send pms. I live in Hervey bay and will be next in Brisbane in early December. I would like the oportunity to see how well it would go with my vehicle if that is possible. I notice you have the rapid hitch - standard. This would probably be enough to solve my issues. Do you know if the rapid hitch - long with the extra adjustment would clear the rear bumper bar?