In the airprox incident that prompted this whole thread it was stated that clear air turbulance caused the aircraft being overtaken to climb through the RVSM levels. It also appears that very smart Eurocontrol people are talking about domestic RVSM. What will happen even at FL300+ when clear air turbulance or predictable mountain waves etc cause these kinds of conditions in greatly more congensted airspace than over the middle of the Atlantic or Pacific? Seems that offsets or some other method of allowing for this type of sudden climb or descent would be a necessary condition to provide a safety margin.