What guidelines apply to the 3D models' alignment to the base imagery in Google Earth?

• Models must be correctly aligned to the underlying imagery published in Google Earth.
• Models must have their height set as relative to the underlying DEM, not absolute; 2.5D and .shp data must have a 3 meter extrusion applied to account for variances in published terrain.
• Models should never float above the terrain when loaded into Google Earth, unless provided with the corresponding DEM they were cut to match.