[Freesurfer] Mask custom ROI with automated parcellation (aparc)

Dear Freesurfers,

Is there a way to mask a custom ROI (or label) with a volume / label from automated parcellations?

I have an overlay with fMRI activations and am only interested in the precentral cortex (as segmented in rh.aparc).

I could do masking either on the label level (fMRI activation label * rh.precentral.label) OR on a volume level (fMRI ROI volume * rh.precentral volume)

ultimately, I would only be interested in surface thickness of my fMRI hotspots limited to the precentral cortex.

So the most elegant way would be if there were a function in mri_segstats that allows outputs of thickness values to be "sorted" by the automated parcellation.

But any help leading there is appreciated!

Best, Bastian