Major in viola performance, minor in violin performance. Is this even possible? Do schools allow you too complete a performance major and minor? Just curious :/
Schools differ--you need to ask them.
Eastman has majors and minors. Usually, students have a minor in something non-performing, e.g, theory, composing, teaching. Before committing to a performing minor, be very clear about the recital requirements. It could be hectic for 2 performing categories. As Scott said, ask each school, and if you are spectacularly good, negotiate. Good schools don't pass up talent.
Major in viola. You have a better chance of being accepted. Then if the school has a secondary instrument requirement see if you can take lessons that way to get credit.