RE: q on isonic and sails
reading one previous post I saw that "... Sail trim was quite "hard" extra 2 cm downhaul and full outhaul. Rig felt beyond limit...". Just thinking: what do you mean by "full outhaul"? Did you make the sail totally flat, so that rig dynamics were killed? Maybe your problems actually have same root there (it seems strange to me that a 5.6 race sail can't take just anything at 78 kg.); a totally flat sail will behave wildly, giving no power and then plenty top end once accellerated. Probably you were slowing down on every chop and having to accellerate again each time. Maybe?