iOS UILaunchImageFile: some 4-inch-screen users see black borders - ios

Question

Some of my users seem to consistently see a clipped screen when running my app on their 4-inch devices. It may be limited to iPod Touch 5g users, and seems to occur on iOS6 and iOS7 (I am still investigating). I have what I think is a simple and correct UILaunchImageFile configuration, and it works fine on my iPhone 5 and in all the simulators. Any ideas?
Info.plist:
...
<key>UILaunchImageFile~ipad</key>
<string>UILaunchImage-iPad</string>
<key>UILaunchImageFile~iphone</key>
<string>UILaunchImage</string>
...
App product filesystem:
MyApp.app/
...
Info.plist
UILaunchImage-568h#2x.png (640x1136)
UILaunchImage-iPad.png (768x1024)
UILaunchImage-iPad#2x.png (1536x2048)
UILaunchImage.png (320x480)
UILaunchImage#2x.png (640x960)
...
[EDIT: my startup code, in MyAppDelegate]
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
...
// screen.bounds is the whole display size;
// screen.applicationFrame is smaller when you show the status bar
UIScreen * screen = [UIScreen mainScreen];
CGRect screenBounds = screen.bounds;
CGRect applicationFrame = screen.applicationFrame;
self.window = [[[UIWindow alloc] initWithFrame:screenBounds] autorelease];
// load main ui
MyUIViewController * main = [[[MyUIViewController alloc] initWithNibName:#"MyUIViewController" bundle:nil] autorelease];
UIView * rootView = [[[UIView alloc] initWithFrame:screenBounds] autorelease];
main.view = rootView;
[main loadIfNeeded];
self.viewController = main;
self.window.rootViewController = self.viewController;
[self.window makeKeyAndVisible];
...
}