Load nib/xib for iphone 5 / Retina 4 Full Screen (568h) custom views, but then default back to ios universal naming conventions (~iphone/~ipad).

ExampleViewController.m

#import "UIViewController+AppCategories.h"

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    nibNameOrNil = [UIViewController nibNamedForDevice:@"ExampleViewController"];
    
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        
        // Do any additional customization 
        
    }
    return self;
}

UIViewController+AppCategories.h

#import <UIKit/UIKit.h>

@interface UIViewController (AppCategories)

+ (NSString*)nibNamedForDevice:(NSString*)name;

@end

UIViewController+AppCategories.m

// ExampleViewController.xib [iphone default when nib named empty for Retina 3.5 Full Screen]
// ExampleViewController-568h.xib [iphone custom naming convention when nib named empty for Retina 4 Full Screen (568h)]
// ExampleViewController~ipad.xib [ipad/ipad mini default when nib named empty]

#import "UIViewController+AppCategories.h"

@implementation UIViewController (AppCategories)

+ (NSString*)nibNamedForDevice:(NSString*)name
{

    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)
    {
        if ([UIScreen mainScreen].bounds.size.height == 568)
        {
            //Check if there a path extension or not
            if (name.pathExtension.length) {
                name = [name stringByReplacingOccurrencesOfString: [NSString stringWithFormat:@".%@", name.pathExtension]
                                                       withString: [NSString stringWithFormat:@"-568h.%@", name.pathExtension ] ];
                
            } else {
                name = [name stringByAppendingString:@"-568h"];
            }
            
 
            // if 568h nib is found
            NSString *nibExists = [[NSBundle mainBundle] pathForResource:name ofType:@"nib"];
            if (nibExists) {
                return name;
            }
            
        }
    }
    
    // just default to ios naming convention
    return Nil;
}

@end