Faking it: step 1: Simplify!

user :      :rw-      ALLOW: :   OWNER@              :rwatTcCy
user :marius:rw-      ALLOW: :  marius@citi.umich.edu:rwatcy
group:      :rw-      ALLOW:g:   GROUP@              :rwatcy
group:staff :rw-      ALLOW:g:   staff@citi.umich.edu:rwatcy
group:users :rw-      ALLOW:g:   users@citi.umich.edu:rwatcy
mask        :rw-
other:      :r--      ALLOW: :EVERYONE@              :rtcy

(Mask example)

user :      :rw-      ALLOW: :   OWNER@              :rwatTcCy
user :marius:rw-      ALLOW: :  marius@citi.umich.edu:rtcy
group:      :rw-      ALLOW:g:   GROUP@              :rtcy
group:staff :rw-      ALLOW:g:   staff@citi.umich.edu:rtcy
group:users :rw-      ALLOW:g:   users@citi.umich.edu:rtcy
mask        :r--
other:      :r--      ALLOW: :EVERYONE@              :rtcy