Per Steve Tyree's assessment, I would be very skeptical of any set formula for stability. I think even novice sailors can trust their instincts: If the weather/water feels threatening, it probably is, because, if you feel like you aren't in control, you probably aren't. Only a durn fool would trust a theoretical stability over his instincts. Conversely, the better the sailor, the better he'll know his boat, understand the conditions and respond to rough conditions. No boat is safe, even the saltiest, most heavily-ballasted globe-girdler, in the hands of an idiot: I know from experience, because I've done positively imbecillic things at the tiller of a Flicka. Light, modern bulb-keeled"cruiser/racers" cross oceans formerly thought navigable only by extremely heavy, full-keeled boats (for my money, I'll take the heavy, full keel), but, in the case of the global challengers, they're skippered by professionals.