How to remove programmatically a tab bar item created in parent class NIB file?

Within my iPhone application I have a common tab bar with three tabs that is presented from several views after pressing a button. The approach I followed was the workflow of Tweetie application, described in Robert Conn post.

Note that the main controller is a navigation controller; the tab bar is placed in a view controller's NIB file of the navigation stack, and the effect of switching between tabs is handled in a delegate didSelectItem method.

@interface GameTabBarController : UIViewController<UITabBarDelegate> {
  UITabBar *tabBar;
  UITabBarItem *lastGameTabBarItem;
  UITabBarItem *previousGamesTabBarItem;
  UITabBarItem *myBetsTabBarItem;

  NSArray *viewControllers;
  UIViewController *currentViewController;
}

@implementation GameTabBarController
  ...

  - (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item {
    UIViewController *viewController = nil;

    // Get the view controller linked to the tab bar item pressed
    ...

    // Switch to the view
    [self.currentViewController.view removeFromSuperview];
    [self.view addSubview:viewController.view];
    self.currentViewController = viewController;
  }

  ...
@end

Since the views of the tab bar must be customized according to the view controller the application came from, I have made this GameTabBarController a parent class with that NIB file that have the tab bar. Then, I have created several children classes:

@interface FirstGameTabBarController : GameTabBarController {
  ...   
}

@interface SecondGameTabBarController : GameTabBarController {
  ...   
}

...

My problem is that in some of the children classes I would like to remove the third tab of the NIB file associated with parent class. But since there is no UITabBarController involved, I cannot follow typica