From the Princess registration page on RunDisney (email link highlighted)......
"Proof-of-Time
New 2014 runDisney proof of time guidelines:
If you believe you will finish the Half Marathon in less than 3:15 hours, proof of time is required for start corral placement. Glass Slipper Challenge participants should adhere to Half Marathon proof of time requirements. Please reference the Pacing Requirements below for finish times and associated pacing per mile.
A proof of time must be provided from a certified race reflecting results after February 1, 2012.
Half Marathon - 10K or longer
A valid proof of time provided at the time of registration must include the following*:
Name of Race
Distance
City
State
Date
Finish time
*For example, Walt Disney World Half Marathon, 13.1, Orlando, FL, 1/12/13, - 2:05
If you do not have a proof of time to submit, list "N/A" at the point of registration. If proof of time is not provided by December 1, 2013 you will be placed in the last start corral. If your proof of time data is incomplete or cannot be verified, you will be placed in the last start corral. To provide or update your proof of time, you must email all proof of time data requested above to disneysports@trackshack.com. No corral changes will be made after December 1, 2013.
As a reminder, you will no longer be able to bring proof of your estimated finish time to the Runner Relations booth during the Expo and have your start corral placement changed.