Securing The Master Db

Hi All,
I am currently creating a SQLServer 7 server. This server will be used to host customer databases that I will restore on to the server. However, I want to prevent these customers accessing any other databases on the server, apart from their own. By removing the public database role from each customer database, and granting them very limited rights (basically exec rights on their own Stored Procs)on their own db, I plan to limit them to their own db. However, my problem is this:
As you cannot remove the public role from the master db, a user could easily exec the following in a stored proc to read from the master:

Select * from master..sysusers

How do I prevent the users from accessing the master in this fashion.
Will removing every permission from the public role in master be enough?
Will removing every permission from the public role in master have any other side effects?
Will removing the public role from other user dbs be enough to secure them?

Any suggestions/pointers would be appreciated.
Gary.