doc clarification

Author: Richard Jones

doc/customizing.txt

@@ -2,7 +2,7 @@
 Customising Roundup
 ===================
 
-:Version: $Revision: 1.146 $
+:Version: $Revision: 1.147 $
 
 .. This document borrows from the ZopeBook section on ZPT. The original is at:
    http://www.zope.org/Documentation/Books/ZopeBook/current/ZPT.stx
@@ -414,8 +414,10 @@ What you can't do to the schema
 You must never:
 
 **Remove the users class**
-  This class is the only *required* class in Roundup. Similarly, its
-  username, password and address properties must never be removed.
+  This class is the only *required* class in Roundup.
+
+**Remove the "username", "address", "password" or "realname" user properties**
+  Various parts of Roundup require these properties. Don't remove them.
 
 **Change the type of a property**
   Property types must *never* be changed - the database simply doesn't take