You need to understand exactly what a WDH actually does first and that is to even the weight distribution correctly over the front and rear axles especially if your towball weight is putting extra load on the towball and tow bar. This can be caused by a few things but mainly the incorrect loading of your van.
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Tug Landcruiser Sahara Turbo Diesel/ Den Luxliner 21' plus
Load and balance your rig. ON THE FLAT. First. fully.
If you sag in the middle a bit.
think about a set of those single/twin round bar units.(built for light vans)
They do a lighter weights job than the reece. which came later.
and only a fraction of the weight.
HR are actually a "bought" modified version of the American "REECE" hitch they brought in from USA.
I still have an old model of such in shed if anybody wants a rusty photo of one.
They are welded together. rather than the pin plates of the HR.
I used 13 S/S 2.5mm rods to fill gap. Remember every one of them in bottomless groove.
If the manufacturers say don't use them don't. A WDH places stresses on the vehicle and the van at points they weren't necessarily designed to take stress. Level the vehicle by packing the van so the back of the vehicle doesn't settle by more than 25mm when the van is attached.
I agree if the maker of the car says not to use them then don't use them, cars that have a hydraulic system for levelling the suspension might be the reason a hitch is not recommended.
but having said that if your driving a car towing a caravan with its nose in the air would not a WDH be a good idea...