A heavier boat only adds half of the extra weight to the righting moment, and multiplied only by the width of the boat: say 10 kgs of extra boat weight give 5kgs*2.5m=12.5 Kgm of righting moment; 10 kg of extra crew weight add 10kg*3.4m=34 kgm, practically the double of righting moment; boat of 2,5m width and crew of 1,8m assumed. This is why extra boat weigth is much more important than extra crew weight. Downwind it gives more or less the same disadvantage, at least for cats that go on two hulls downwind.

From my personal experience I we have found that older sails don't pay on a older boats in all but very light wind conditions. We gained a lot when we got new sails on our 1991 H16.