bsdgroups?

["x" <x@xxxxxxxxx>]

In the future, do you plan to support 'bsdgroups' ?

grpid or bsdgroups / nogrpid or sysvgroups
              These options define what group id a newly  created
              file  gets.   When grpid is set, it takes the group
              id of the directory in which it is created;  other­
              wise  (the  default) it takes the fsgid of the cur­
              rent process, unless the directory has  the  setgid
              bit  set,  in  which case it takes the gid from the
              parent directory, and also gets the setgid bit  set
              if it is a directory itself.

Thanks
-Garrett