Genghis,
You said:
So, a microlight must have an empty weight not greater than MAUW - 86kg/seat - 1hrs fuel at maximum continuous power. This is identical to the requirement in CS.VLA for non-aerobatic light aeroplanes
To my reading all that does is set a maximum weight for the aircraft structure (including engine).
Where in relation to the above limitation does it say that having a structure that meets that requirement, it is illegal for each seat to be filled by 96Kg individuals and the fuel load reduced so that MTOM and C of G limitations are complied with?
Does the seat limit only arise because the designer has designd a placard showing a limitation?
Having had some time to think about it, I think that I would prefer to be sitting on a seat whose legs would crumple under me in an accident than be sitting on a seat that would hold firm and transmit all the shock load to my spine.
Regards,
DFC