Actually you can resize the view controller that gets presented with UIModalPresentationPageSheet. To do it you need to create a custom view controller class and add the following to the class:
<!--The header file-->
@interface MyViewController: ViewController{
  //Used to store the bounds of the viewController
  CGRect realBounds;
}
<!--In the .m file-->
//viewDidLoad gets called before viewWillAppear, so we make our changes here
-(void)viewDidLoad{
    //Here you can modify the new frame as you like. Multiply the 
    //values or add/subtract to change the size of the viewController.
    CGRect newFrame = CGRectMake(self.view.frame.origin.x, 
                                 self.view.frame.origin.y,       
                                 self.view.frame.size.width, 
                                 self.view.frame.size.height); 
    [self.view setFrame:newFrame];
    //Now the bounds have changed so we save them to be used later on
    _realBounds = self.view.bounds;
    [super viewDidLoad];
}
//viewWillAppear gets called after viewDidLoad so we use the changes 
//implemented above here
-(void)viewWillAppear:(BOOL)animated{
    //UIModalpresentationPageSheet is the superview and we change 
    //its bounds here to match the UIViewController view's bounds.
    [super viewWillAppear:animated];
    self.view.superview.bounds = realBounds;
}
And then you display this view controller with a UIModalPresentationPageSheet. And that's it. This does work for iOS 5.1.1 and iOS 6 as of the date of this post.