Miter corners in sheet metal with radius bends

I've got a sheet metal problem. My part has radius bends that terminate in mitered corners. When I flatten the part, the flat pattern does not properly adjust the edge for the bend. I sketched in red what the edges more or less should look like. The straight line is a reasonable approximation for small radius bends, but fails miserably for large bends. Fixable in sheet metal or do I need to use the Flatten Surface command to get the correct curve?

SolidworksSheet Metal