Thanks Daniel.
The volumes have already been through @Align_Centers, so overlap with the MNI template is high. I use the -plusminus option of 3dQwarp to form the subject-specific template from two visits in time. There doesn't seem to be an option in 3dQwarp to provide a -master data set (i.e., the MNI template) for the output grid, so I'll reslice the result in a separate step.
Thanks for the clarifications!
- Daniel