Flat rate boxes cost $8.10, regardless of weight. Whatever you send must just fit in one of the two box sizes that are available.
I think I was thinking of smaller flags. I'm going to buy and send today so will have more cost analysis later.
As I posted on the other thread, I love the idea of this, but please keep in mind that what you are sending may not be delivered for weeks, I'm told, because everything sent to D.C. leadership is still being irradiated :(