[Freesurfer] longitudinal stream percentage change

Dear freesurfer-experts,

I have successfully done a longitudinal analysis on cortical thickness changes over 2 timepoints (0 and 1 year).

My question is:

If I look at the -individual- overlays of perc. change (i.e. pc1fit), only positive values are shown. whereas at the -fsaverage- view, positve AND negative values are shown (i.e. thinning and thickening)

I understood that long_mris_slopes calculates the "percent thinning per year". But is there a way to show both sides of the histogramm (i.e. from -2 to +2) also on the -individual- overlay?

This might be a naive question, however, any help is greatly appreciated!

Bastian.