Christian Gaser made the following comment on non-stationary correction in SPM8.
Furthermore, SPM8 (release >= 4010) provides a non-stationarity correction, that is based on smoothed RPV-maps, which should be more reliable than the unsmoothed RPV maps in VBM8 or in the NS-toolbox. To enable this function set:
defaults.stats.rft.nonstat = 1;
in spm_defaults. However, this option will result in a much longer calculation if you print the results table.
This is maybe also the reason that this option is not set as default.