[Freesurfer] How can I convert an individual subject's mask to the group average space

All,

I have generated a mask of the cingulate regions for each of my participants from their aparc+aseg.mgz files (see attached image) and I would like see how these masks overlay with the group average brain I have generated for my study. Is there a simple way to transform a mask from an individual subjects space to the group average volume space? I made my group average with the make_average_subject command.

In a related question is it possible to generate a group average aparc+aseg.mgz file? I can see the surface labels in the average and the aseg.mgz cortical labels. However, I don't know of a way to generate the aparc+aseg.mgz file.

Thanks for any help you can offer, Avram