My trailer is an aluminium box trailer, I don’t know the exact ball weight, but it would be less than 100kg I reckon.
100 kgs is not going to cause any problems providing you never load the tub to its maximum plus a bit more like many owners do. That is when the bent chassis problems can really upset your day.
One very important thing with towing is always read the towing instructions in the car's handbook and never go against them.
It seems that in regard to suspension a lot of people just put a two inch lift in so it’s a ‘proper 4wd’, but I wonder how many actually need it
I think a lot of it comes from saturation advertising in magazines and the DVDs that come with them. I suppose you can't blame them though. They must have sponsers to fund their magazines and they must keep their products selling if they want to keep them.
Then there is the 4WD expos. Just a few minutes in one of them is enough to convince anyone that every part of a new car is so inadequate for any road except your driveway.
Of course there are tracks that are so rough that you do need suspension alterations but they are few and far between. You can see about 95 % of the country without them.
If you find yourself in a situation where a modified suspension is necessary, then speak to a suspension company that really does understand suspension design and can explain what the alterations are going to do on sealed roads.
As an example, I was very interested in motor racing in my very much younger days and I bought many editions of Racing Car News magazines. In the for sale section for competition sedans and sports cars, the description for many cars often included the words " Heasman suspension".
Heasman is a Sydney suspension company that started in 1954 and are still in business and owned by the same family today. They can modify anything from a ute to a new Ferrari. That is the type of company I would go to.