That's why I load 2.7 tonne, to allow for the trailer weight, and why a 2.7t digger is the heaviest you can legally tow as you correctly say there is at least 1/2 a tonne in the trailer. How you are loaded is also critical, in the flat beds the loader drivers will try to get the load as central as possible. Which means that the nose load is kept fairly consistent however sometimes they get it wrong. But you are also correct, that ensuring you aren't too nose heavy is critical for handling. It's trickier to gauge in the air suspended cars too, as they will self level, so the tow bar is always at the right height even if it has too much on it.

It comes down to experience, loading, and speed and also the type of car. 90's tow well even though they weigh in at under 2t as the have a really short rear overhang. So the hitch point is closer to the rear axle than on other vehicles giving the trailer less purchase on the rear end making them more stable than their weight would indicate. But even so personally I personally wouldn't want 3500kg on the back of something which has a kerb weight of less than 2 tonnes for any great period of time.

I find it really interesting that many trailer manufacturers don't put a tare weight on their trailers. Having to weigh it yourself on a weighbridge is a bit of a pain. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
KIA E-Niro 4+
2021 Discovery 5 D300 MHEV commercial