How can I force all clients to use the same file mappings?

[AndrewDalgleishandrewd at axonet.com.au]

We are currently using source safe, and we have made some (but not
extensive) use of it's file sharing to have one file appear in more than
one directory.
Using source safe, if a file is shared for one user, it is shared for
all users.

I understand that Perforce can do this using file mappings in the client
definition.
My question is, how can I force all clients to use the same file
mappings?

Do I send an email to all developers and hope they don't ignore it?
Should I edit all client definitions from my own PC?
Is there a "#include" type of feature?

Regards,
Andrew Dalgleish