MyFiles question

Trying to figure out how space to give the 2nd disk for our Filr setup. From what I read, it really depends on if we will be letting users use the MyFiles portion of Filr. By default we will have MyFiles default to their home directory so no space will be used there. Now some of our users may have some interaction with outside company's and may want to share files with them. Now I know if an outside user shares files they will be stored on that 2nd VM disk, right? What happens if one of our users wants to share files from their home directory with an outside user? Where are they stored?

One more question. Is there some sort of auto-delete that can be used for the "MyFiles" section, not the home directory but the space that is used on the 2nd disk itself?

Thanks,
Scott