For porous materials there exists a percolation threshold (which is zero for some models), below which the structure becomes disconnected. As the threshold is approached, the elastic properties become dependent on small tenuous connections, which are increasingly difficult to resolve. Moreover, for models with a non-zero percolation threshold, percolation theory implies that the connections are separated by an increasing distance, which leads to large statistical errors. Both these factors place a lower limit on the volume fractions at which we could accurately estimate the elastic properties. For models with a finite threshold, we only considered volume fractions such that p - pc > 0.1.