The idea of F18 is not to have faster boat (180 kg is not very performing indeed). Faster boat have no interest in the game. The idea is to have very close boats.
A class or C class are box rules and are developpment series, always improving your boat to go faster is part of the game.
F18 genuine idea is not that.
F18 is a close class rules. What is not allowed is forbidden.
That is the F18 spirit. So twisting the rule is not right and contain evolution logical.
Due to the success of F18 and some hole in the original set of rules (height of hull, length of daggerboard) and some authorisation (carbon in daggerboard, without it you cannot have thin and 2 meters daggerboard), you have now 2 or 3 F18 fleet.
So a Tiger can no more win a national F18 Championship (last time in Spain in 2010). That is a warning.
And that bad move explain: C1, C2, C2 with longer daggerboard, Infusion , Infusion MK2, Wildcat with new set of sails and so on. This is a run that made your F18 obsolete.
Some details like moving from gel coat to paint to gain on structure weight or using very light sails (the subject of the topic) make a gain of performance.
It's easy to understand the wish of a faster boat. But having a faster F18 is not the target. That is less interesting than improving sailing skills.