If your primary application is more or less ready to go with the exception of pending MCAT scores, I would go ahead and submit to ONE throwaway school (i.e. one you would be happy to attend, but not at the top of your list). If your scores don't turn out as well as you'd hoped, you'll have minimized the amount squandered on application fees, and if you have to reapply next year, you will only be considered a re-applicant - a potentially detrimental status - at that one school. If, on the other hand, you are satisfied with your scores, your primary app will have already been verified and you can designate more schools at your discretion. Having already been verified will allow your application to be processed 5-6 weeks sooner than it otherwise would have been, and timing is critical at this point in the application season.