At $1.90 each for the SS Hobie nut, I could buy a handful of the plastic nuts and let them split as they wish. And it would be impossible to overtighten them.

If you use solid nuts, how much play should you allow for thermal expansion and contraction? Would using a stainless split-lock washer that is not completely tightened be the better way? (Maybe I should just buy a 1/2"-13 tap and make my own nuts.)