Maintaining an Elgg session across sub domains

I have seen a lot of people ask this question on the web and here in the community, but I have yet to find a solid answer. I am trying to maintain one elgg session accross multiple subdomains such as:

docs.elgg.org and community.elgg.org.

With other applications and sites I've built, this solution has helped, but it does not work with Elgg.

http://www.epigroove.com/posts/87/using_php_sessions_across_subdomains

I am assuming Elgg is setting the session cookie in a way that I need to modify. Any ideas or help? Thanks in advance.