NO, you are exactly right. You can remove the everyone group and only add specific users. However, you probably want to restrict access to the drive that the user data resides on. The SYS colume is kind of important because when a user authenticates, there are specific NETWARE files in the SYS:SYSTEM and other SYS: directories that users need to have access to.
Just remember that unlike Microsoft, Novell is usually locked down so that users just don't have rights. You also have to remember that rights flow down the directory structure so there is a chance that the 'Everyone' may be getting their rights from a higher point in the NDS tree. Its not that hard to figure out, just check the rights to files and directories for the everyone group and you can confirm what is coming from where.
HTH
Mark C. Greenwood, CNE
m_jgreenwood@yahoo.com
With more than 10 years experience to share.