As has already been said, hereabouts, it's just only better than a crap shoot. You can never have too much rode out until you bump the shore or the guy behind you. You can never have better conditions than one foot more than your draft, no tidal influence, and just breeze enough to keep the blood suckers away. After that everything influences what to use and how much. I've used all line rode, some line and some chain and on several occasions all chain on one particular vessel. The best bet is to get the very best you can, and as much of that as you can find, (and still float) and call it insurance. That includes everything, from the mud to the cleat. That's why we endeavor to make this sort of decision anyway. It's for our safety but mostly for HER piece of mind (and thereby yours [and I'm not talking about the first mate]) .