keep in mind that a nacra usually has a lot more hull volume than an equivalent sized hobie, but much the same weight

meaning those larger nacra hulls must be made thinner

also i think most/all? hobies have been made with the foam sandwich technique which is stiffer than the early 80's nacra single glass layup

so in general a 1983 hobie hull will feel stiffer all over than a 1983 nacra hull

so if both your nacra hulls seem to flex the same amount all over the boat then they are either completely stuffed, and beyond saving, or it is quite normal for a nacra