I believe if it was such a great design, there would be many more companies making them and more of them out there.
As I recall, there was a company in Bundaberg producing them years ago.. The essence of why there arn't a lot around is due to the manufacturing process.
The body is rotational moulded which is a similar process to manufacturing plastic water tanks. As people that are familiar with this process would realise is
that it requires a rather large rotating mould. Second to that, because there are corners in the design as opposed to a round water tank, a lot more of the HDPE
material is required to ensure that all corners of the mould accumulate enough material during the rotating process to achieve the required wall thickness of
the product. This leads to a more then necessary heavy product, and lot more material cost and a longer production time. Which in turn, leads up to an expensive
product. Also, when the body is fitted to a chassis, the whole trailer adds up to a substantial weight which is usually much more then a steel sided trailer.
This made the idea non competitive with the average box trailer. I have known of a few people that bought the bodies (freight cost needed to be included) and
built their own chassis. In all cases, last I heard, the trailers were going strong after being to the Cape and another to the Kimberlies.. If you think about it, makes
sense as they and strong and rust free. To stop side scraping damage off road, riveting thin alloy chequer plate would suffice for protection. As long as you have a
big enough vehicle to tow the trailer mass.
So, I guess, there was never enough volume to justify the larger rotational moulding companies getting interested..