i'm developing app for both IOS7 & IOS8, and using storyBoard with size classes enabled.
app works fine in all simulators from iPhone 4s IOS7 to iPhone 6+ but the viewController is smaller than the screen in iPhone 5 with iOS7
app supports different orientations, i tried and canceled orientations but didn't work. i rested the simulator content, didn't work. I tried to change the initial view controller, didn't work. I cleaned the project, didn't work
To run your application in fullscreen in iPhone5 you must provide Launch Image for iPhone5 with resolution 640x1136
.
If you are not including Launch Image of the size iPhone5 require then app will run in the centre of the screen, showing black area at top and bottom.
You can also refer here for more information.