I haven't done C2C yet, so I could be way off. That being said, I noticed the question about C2C on the registration for marathon weekend, and clicked yes since I plan to participate this year. I know Disney is big into trying to talk people into running other Disney races while they are at a different event weekend, so not everyone will know they are doing c2c when they register for race #1. I bet the really important time to mention on registration that you are running c2c would be on the race form for the second coast's race. If you don't mention it on your registration, I'm sure you can go to a booth at the expo and they can look you up and verify that you are going to complete c2c.