It think some of the "light feel" of the newer Sterns has a lot to do with the thinner gauge steel in the legs. They certainly twist more that my WPC legs contributing to an easier to nudge feeling. My games are on carpet, so I can't move them around by nudging aggressively.

That said my WPC legs look like a thinner gauge steel than my older Bally legs, so I guess this type of cost cutting has been going on for a longer time than we think. This is most likely the reason, starting around the System 11 days, they started putting ribs on all their legs to increase stability..

Indeed