Below is an excerpt from SPM-ML
There is an option for the newest SPM8 releases (>=4010), which enables non-stationarity
correction on the cluster level. Please set in spm_defaults.m:
defaults.stats.rft.nonstat = 1;
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.