Ryan:FGeometryCollectionPhysicsProxyneeds access toGeometrySharedLowLevel(), as it needs access for the same reason as ParticleData. For some reason the friend declaration isn't working. Exposing this function until this can be straightened out. friend classFGeometryCollectionPhysicsProxy; This is only for use by ParticleData. This should be called only in one place, when the geometry is being copied from GT to PT.