I fitted a bolt to my factory setup on one of my tow ponies.
Foward of the pin so it pushes up holding the ball end down.
I only use it in limited situations as I'm regularly swaping the tounge and tow receiver.
1 use for the bolt is our dog trailer.
The ball wieght is @30kg and it rattles, I'm going to re-chassis it moving the axle to the rear.
The only other time I bolt it tight is when on longer off road trips.
This is only to stop any movment as the hitch wieght changes over conservation mounds or cresting sand dunes etc..
Back the Op's post...
As I've said we swaped to a DO35.
I've used it on 2 trips and it did all it was supposed to testing it at the river crossing at the potato patch.
I've moved the van a couple of times at home and it is sooo easy to hook up.
Only down side is the plastic cord to save the cover if it falls off looks weak.
I may upgrade it to a steel one(fishing trace or 4mm electric wire).

