The reality is that on a modern microlight (I owned a CT for 5 years) the MTOW was seldom an issue. True with 2 adults the maths is very simple from memory - CAA limited 450KG max and 268KG max empty leaves very little for fuel. The CT however can take 130 litres of fuel which would put it way over weight with 2 up.
The CT however is a great performer and can safely (but illegally in UK) take 2 adults and a lot of fuel. Its more a regulation issue than performance as the same aircraft can legally fly at a much higher MTOW in other countries.