If its an unbraked trailer the max weight inc trailer is 750 kg. Not sure of the new laws regarding test to tow.
As a guide my Aircraft is 350 kg (dry weight) + engine 115 kg + trailer unbraked 240 kg Total weight 705 kg.
The only thing is that I have to be careful with fuel and what else I load on my rib as I am left with only 45 kg to be road legal legal.
So to answer your first question I would say yes it weighs less than 750 kg