I understand that adcoms are actually allowed the info to find out if a student is holding spots at mroe than 1 school after May 15, and can contact the other school(s) and the student. If this is true, than I guess a school could choose to enforce the rule, and I imagine it just depends on the school. If you are waiting on financial aid info, I'm sure the schools would be willing to work with you if you explain the situation. I've found that adcoms become much more accomodating after they've accepted you. 🙂