Thinking back, I believe most of the calls we have gotten in ribs this year came from ribs I thought I had overcooked. Everyone, including judges loves them fall off the bone, even if they won't admit it. You almost have to cook to falloff the bone since they do tighten back up a bit when they cool.
Have tried mustard and safflower oil (the spices in rubs generally aren't water soluble but are oil soluble) but really couldn't tell it helped. We just sprinkle heavy, pat till the rub is moist and not dry, then sprinkle lightly again. We do this 1 hour before cooking.