ScrolledComposite parent with GridLayout

I'd like to have a ScrolledComposite which has a parent with GridLayout but the scrollbar doesn't show up, unless I use FillLayout. My problem with FillLayout is that its children takes equal parts of the available space.

In my case there are two widgets, the one on top should take not more than 1/4 of the window and the ScrolledComposite should take the remainder space. However, both of them take half of it.

Is there a way to use a GridLayout with ScrolledComposite or is it possible to modify the behaviour of FillLayout?

Here's my code:

private void initContent() {

    //GridLayout shellLayout = new GridLayout();
    //shellLayout.numColumns = 1;
    //shellLayout.verticalSpacing = 10;
    //shell.setLayout(shellLayout);
    shell.setLayout(new FillLayout(SWT.VERTICAL));

    searchComposite = new SearchComposite(shell, SWT.NONE);
    searchComposite.getSearchButton().addListener(SWT.Selection, this);

    ScrolledComposite scroll = new ScrolledComposite(shell, SWT.V_SCROLL | SWT.H_SCROLL | SWT.BORDER);
    scroll.setLayout(new GridLayout(1, true));

    Composite scrollContent = new Composite(scroll, SWT.NONE);
    scrollContent.setLayout(new GridLayout(1, true));

    for (ChangeDescription description : getChanges(false)) {
        ChangesComposite cc = new ChangesComposite(scrollContent, description);
    }

    scroll.setMinSize(scrollContent.computeSize(SWT.DEFAULT, SWT.DEFAULT));
    scroll.setContent(scrollContent);
    scroll.setExpandVertical(true);
    scroll.setExpandHorizontal(true);
    scroll.setAlwaysShowScrollBars(true);

}