You bring up a good point with the dual-degree students. Definitely something to consider when it comes to financial aid. Also, don't forget that if you do decide to pursue a dual degree, in some programs, you have to take a leave of absence from the med school and pay tuition to the other program (e.g., School of Public Policy, UNC's School of Public Health); if there's a price difference, you'll have to factor that into your plans, as well.
In another thread, one of the current students also mentioned that there are a number of scholarships that go unclaimed each year. Assuming it's for a field you're interested in, it's mostly a matter of paying attention to all the announcements and staying on top of deadlines. Also, in talking to the first and second years at Second Look, I got the impression that many of them felt that funding for third year was actually pretty easy to get, again, provided that you stay on top of deadlines, put in the effort, etc.