there are programs that tell you the angle of the sun at different seasons for different locations. you'll likely have to do the geometry yourself, but it isn't terrible.
around here, it seems like using eaves for this purpose doesn't work real well. it's typically well into June before the sun gets intense
enough to cause problems. so we use deciduous vines instead. they seem to fit the seasons better than relying on the angle of the sun. Missouri will likely be substantially different than southwest Washington, though.