gistfile1.m

CCMenuItemImage *menuItem = [CCMenuItemImage ...];

// Make touch area centered and 4 times smaller than bounding box 
menuItem.touchArea = CGRectMake(
                                            menuItem.contentSize.width/4,
                                            menuItem.contentSize.height/4,
                                            menuItem.contentSize.width/2,
                                            menuItem.contentSize.height/2);