Most First National flags of the period DO have stars on both sides - the overwhelming majority of them! There are exceptions and they number in the handful range so far based on known flags. I know of an FN in Kansas that has a woman drawn on one side of the canton and the stars are on the other. Mississippi has an FN with the unit name on one side f the canton and stars on the other.
By contrast, about all of the Ebay fakes have no stars on the reverse side of the canton.
Greg Biggs