Also consider setting AFNI_PBAR_THREE to YES. You can try that out with "afni -DAFNI_PBAR_THREE=YES". That allows you to remap the Overlay sub-brick display to have lower and upper limits. The colorbar will have "sashes" attached to drag. Left click on the solid bands of color above and below the colorbar for options on whether to color with the ends of the color scale or not.