afni.nimh.nih.gov

I've run some structural data through the VBM8 (SPM8 toolbox) and then run into trouble with running 3dttest++ on the resulting files. I've used this procedure before (since I prefer to operate in AFNI land). Essentially when I load the overlay stats over a mean image (made with 3dMean), I end up with the stats image looking considerably larger than the underlay (see below). Running nifti_tool on the files shows that they really aren't that different. Any tips would be appreciated.

nifti_tool -diff_hdr -infile ave.nii.gz stats.nii.gz 
  name                offset  nvals  values
  ------------------- ------  -----  ------
  dim                   40      8    3 121 145 121 1 1 1 1
  dim                   40      8    5 121 145 121 1 6 1 1
  vox_offset           108      1    3168.0
  vox_offset           108      1    10560.0