In our home shops, with often large temperature changes, we do not always attain the stated accuracy of the plates. It is not just the swings in temperature, it it is the diurnal (day/night) changes that cause stratification of the plate temperatures. The top surface can be warmer or colder than the bottom surface with temperature swings, and that causes significant warping of the plate. Open stands, where air can easily churn around, help to get the air in the shop to all the plate surfaces, and then you are only dealing with the actual stratification of the temperatures in the shop which affect it. Hot lights, sun from a window, open doors, air conditioner and heat outlets, and other transitory temperature changes are the big culprits. A surface plate with all the surfaces holding the same temperature will be quite close even if the overall temperature changes from higher to lower. Less stresses...