checking for an iOS 4inch versus a 3.5 inch screen http://stackoverflow.com/questions/13102054/load-different-storyboard-for-iphone-5-app-start

resizeForiOS5.m

if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPhone)
    {    // The iOS device = iPhone or iPod Touch


        CGSize iOSDeviceScreenSize = [[UIScreen mainScreen] bounds].size;

        if (iOSDeviceScreenSize.height == 480)
        {   // iPhone 3GS, 4, and 4S and iPod Touch 3rd and 4th generation: 3.5 inch screen (diagonally measured)

            // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone35
            UIStoryboard *iPhone35Storyboard = [UIStoryboard storyboardWithName:@"Storyboard_iPhone35" bundle:nil];

            // Instantiate the initial view controller object from the storyboard
            UIViewController *initialViewController = [iPhone35Storyboard instantiateInitialViewController];

            // Instantiate a UIWindow object and initialize it with the screen size of the iOS device
            self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

            // Set the initial view controller to be the root view controller of the window object
            self.window.rootViewController  = initialViewController;

            // Set the window object to be the key window and show it
            [self.window makeKeyAndVisible];
        }

        if (iOSDeviceScreenSize.height == 568)
        {   // iPhone 5 and iPod Touch 5th generation: 4 inch screen (diagonally measured)

            // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone4
            UIStoryboard *iPhone4Storyboard = [UIStoryboard storyboardWithName:@"Storyboard_iPhone4" bundle:nil];

            // Instantiate the initial view controller object from the storyboard
            UIViewController *initialViewController = [iPhone4Storyboard instantiateInitialViewController];

            // Instantiate a UIWindow object and initialize it with the screen size of the iOS device
            self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

            // Set the initial view controller to be the root view controller of the window object
            self.window.rootViewController  = initialViewController;

            // Set the window object to be the key window and show it
            [self.window makeKeyAndVisible];
        }

    } else if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)

    {   // The iOS device = iPad

        UISplitViewController *splitViewController = (UISplitViewController *)self.window.rootViewController;
        UINavigationController *navigationController = [splitViewController.viewControllers lastObject];
        splitViewController.delegate = (id)navigationController.topViewController;

    }

This is an unwiedly way to do it -- i have a ternary version which i'll post up for other beginners.