remember that if it is rust that you are worried about that you need air for it to happen. no air means no rust. so i like the idea previously mentioned of pouring clean engine oil
down into the bilge
and then letting it work its way into all the cracks and crevices. then just degrease the top and put an inch or fresh concrete over the top and it is sealed forever. concrete has the right ph level to inhibit rust, so you have two factors working for you to stop any rust from getting any worse.
as for changing the design of your boat...i'd definitely check with the owners association, or the original designers...good boats are carefully designed and i'd be surprised if an amateur fix would resolve a problem, unless the boat was built incorrectly in the first place.
sailboats are very different beasts from the old fashioned heavy displacement
boats, and each performs differently in different conditions as a result. the lighter boat will be quick and responsive but you might not like the way it sails
in big seas day after day because it will be very draining to keep under control. the heavy displacement boat will be slow and not much good for an afternoon race
in light air, but she'll be very comfortable and easy to sail in bigger weather
. horses for courses!