Thanks for your hints, but I cannot change the tongue, because the trailer is approved by the authorities and a change needs a new approval and the engineer will not accept to change the certified tongue and coupler.
In USA you can use different couplers (small ball or pin) for attaching a trailer to a bike.
Some of them may work better with a pivoting tongue. But safety chains must be used.
In Europe the 50-mm-steel ball is the only certified connection.
It is proven safe up to 3.5 tons and we need no safety chains here.
From the smallest trailer up to towing motoryachts it is the same.
The freedom of moving around the ball is VERY BIG, so that heavy caravans
have often special couplers which "clamp" the degreased ball and make the connection stiffer, to prevent the trailer from shaking, if a Mercedes Sprinter passes with 160 km/h.
I will not drive much on highways with this trailer.
And I will find the safety zone with try and error like with my fullsize trailer.
In France you are allowed to go with 130 km/h on highways with a caravan
and if the balance and tongue weight is correct, that was never a safety problem.
I know the influence of a passed truck or passing coach and I am sure I will find my way home safe.