2 Questions about layouts

Hi all. I've got 2 questions about layouts: I have the layout system shown in the image that I have attached with this thread: In the main layout (white color) I've got three sublayouts (green, red and yellow). The layouts in black and grey are sublayouts of the green and red layouts. Well, in my program there's an option to hide the green or red layout in any moment. And here are my questions:
1) Why when I try to hide for example the red layout, the space between the green and yellow layouts is greater than the spacing that I've defined for the main layout? And equally if I try to hide the green layout this space appears in the top of the red layout. Isn't it possible to completely hide a layout? I've tried it setting the margins and the spacing in the layouts to 0 but always appears the spaces. Anybody knows why?
2) Is it a faster way to hide all the objects in a layout than calling for every object the hide or setVisible(false) functions?

Thanks.