Symmetry tolerance

I've got several projects where my models have a lot of symmetry going on.  Specifically, I've got several parts where there is a square boss that is centered on a square surface.  What I would like to do is use geometric tolerance to locate the boss.  But all I have been able to do is locate edges to edges.  Does any one know a better way of setting up the DimXpert for this part?

Thank you,

Joseph Alston

SolidworksTolanalyst And Dimxpert