Yup, you can. I did it, and I’ve had two advisors for my major. You can even mail the form in over the summer, although I would definitely recommend going to the Registrar’s office (you get a button!)
Another thing - do not despair if classes are offered at the same time. One of the virtues of going to a small school is that there are often options - I had two important classes this semesters which had conflicting 4th hours, and one of my professors was willing to create another section of the 4th hour so I could take the class. That isn’t always the case, but it does happen.