Hi Doug,
I attached a .png file to show an example. The Yellow outline is the right and left caudate surface. The right surface (yellow) was created by using 3dLRflip (Afni program) to symmetrically flip the volumetric ROI so that I can create the right caudate surface from scratch again. The blue outline is the same right caudate surface created when I used mris_reverse on the left hemisphere surface. As you can see the blue surface outline is not exactly symmetrical, but rather it is shifted to the left by one voxel. This was noted in some earlier posts regarding mris_reverse from 2004 as an issue (
https://www.mail-archive.com/search?l=freesurfer@nmr.mgh.harvard.edu&q=subject:%22\[Freesurfer\]+R+L+flipping%22&o=newest&f=1).
I was curious to see if xhemireg or the surfreg methods alleviate this issue, or if there is another set of preferred commands to symmetrically L-R flip the brain?