Hiding controls changes spacing of other controls

Hi,

Created in Designer.
I have 5 slider controls arranged vertically in a group box.
They all have a size policy of Fixed.
The containing Group Box also has a size Policy of fixed.

In some instances I need to hide one or more of the slider controls.
When I do that the slider controls change their position so that
ones still displayed are spaced evenly in the vertical direction.
ie.

1-------
2-------
3-------
4-------
5-------

becomes
1-------

2-------

3-------

That's nice, but not what I want. I want the sliders to retain their
original position and have the extra space below them where the other
controls are now hidden.

How can I enforce this?

Thanks

Mark