Preferred location for server config file in install

Hello,
Our product requires a configuration file (XML) to be loaded at server start-up. The content is too rich to be added to the teamserver.properties.
I have two questions. First, what is the recommended location in the install to lay down configuration files? The file is end-user editable so it can not be bundled into one of our plug-ins. Also, is there an established approach to get access to this location (i.e. a system property indicating server root, etc)?
Thanks for the advice.