Here is a link to another thread that talks about the MARCO Marathon Calculator.

http://www.runningahead.com/groups/LOWHRTR/Forum/Post/f93e4bc8777741f2be6906143b4cf718#focus

It might help you with your pacing in the event.

Well, I went for it and I did it! I followed MARCO's pacing pretty closely and had a heck of a negative split... last half was 9:53 seconds faster than the first half. Overall time 6:29:55, beating my goal of 6:30:00.

Thanks, everyone!