The idea is to set AFNI_GLOBAL_SESSION to the name of your group directory. Then all its contents will be visible to all other session lists. Then open 2 controller windows, Switch Session in each to the subject you want to look at. In the [A] controller (say), make the function be from the global session and in the
controller, make the function be the individual's data. This should work, at least in Talairach coords.
As to why symbolic links aren't working, it may be because you have to make a link to the .HEAD and to the .BRIK file for each dataset?
bob cox