Ive sailed heavy boats and light boats old and new designs, long keels, deep keels, bilge keels and no keels, made of wood, steel, grp and concrete in all weathers. IMHO the if the old ones were so wonderful then the new ones would be that shape. But they're not, things have moved on and provided you buy a boat that manufacturer thinks is fit for your purpose then it will be. There are various measures you can use as a GUIDE, like STIX and category and they make sense as a starting point. My experience of crockery breaking conditions in any boat is pretty similar, in old designs perhaps a periscope would be appropriate as they tend to go through the sea rather than on it, but overall its the sea not the boat that breaks stuff, and most boats exist in the, at times, rather troubled 3 or 4 meters of the surface - not a comfortable place to be in anything when its rough IMHO that is!

The only microwave cooker I have seen ever "lost" was on a 70ft steel boat where the skipper was so convinced that his boat would somehow smooth out the 4 meter waves that he didnt tie it down, even when its lack of attachment was pointed out! With its loss came the usual comment "if you think this is bad think yourself lucky you're not in a new boat", I was thinking that on a new boat we would have been 100 miles further on perhaps out of this weather altogether and enjoying a hot something and not being drenched by every wave that tended to break over this very ponderous tin thing.