I guess this works as well.
which would be the 2nd question, how much should we be messing around in the "lib" directory?
Your solution above seems fine to me but I'm no UI expert. If you change the class in lib, then it will apply this styling to all list views with the class "listview-stylingless". So to answer your questions, I only mess around with classes in the lib folder when I want to make a global change. Otherwise I create a custom class in the custom sass file.