Seems like the way to stay within the rules is to apply to Vanderbilt RD by 12/1, then switch to ED 2 if Stanford rejects. Of course, that depends on whether Vanderbilt allows changing an RD application to an ED 2 application after it is initially submitted.
Switching to ED 2 may also reduce the chance for a merit scholarship, since Vanderbilt need not compete with money to get you to enroll.