[Freesurfer] applying longitudinal processing on twins

Dear FreeSurfers,

I'm about to analyze cortical thickness in monozygotic twins discordant for certain expertise. The within-pair similarities in brain morphology are striking (e.g. twin1 x twin2 intracranial volume correlation r=.99) and you could easily play a memory game with the images. Nonetheless, there are notable within-pair differences in gyrification etc. I'm trying to figure out if the longitudinal stream, or some version of it, might still be a viable option in this situation. The sample is fairly small and I want to do what I can to maximize sensitivity. Do any of you have experience with a similar data set or ideas/opinions/recommendations?

Best regards,

Örjan