correct way to do absolute layout in view cells

I was doing this in my cell xaml:
<?xml version="1.0" encoding="UTF-8"?>




<xlabs:GridView.ItemTemplate>



</xlabs:GridView.ItemTemplate>

            </ViewCell>

I then have this in my code behind

    public PanelCategoryCell ()
    {
        InitializeComponent ();
        var accountManager = Resolver.Resolve < AccountManager > ();
        var size = AppHelper.ScreenSize;

        //TODO this isn't ideal, as it's not top down layout
        AbsoluteLayout.SetLayoutFlags (CategoryLabel, AbsoluteLayoutFlags.None);
        AbsoluteLayout.SetLayoutFlags (VideosGrid, AbsoluteLayoutFlags.None);
        AbsoluteLayout.SetLayoutFlags (VideosGrid, AbsoluteLayoutFlags.None);

        CategoryLabel.Layout (new Rectangle (0, 0, size.Width, 20));
        VideosGrid.Layout (new Rectangle (0, 20, size.Width, CellHeight - 20));

        _spinner = new ActivityIndicator () {
            Color = Color.White,
            IsRunning = false,
        };
        _items = new ObservableCollection<IVideo> ();
        AbsoluteLayout.SetLayoutFlags (_spinner, AbsoluteLayoutFlags.None);
        Layout.Children.Add (_spinner, new Rectangle (140, 60, 40, 40));
        var category = new VideoCategory () {
            Name = "SPORTS",
        };

        LoadVideos (category);
    }

It just totally ignores my layout calls, and fails to lay things out as I specify and doens't set width or height on the label.

how are we meant to create layout children in xaml; but change their sizes in code, inside of a viewcell. I would imagine this is a very common thing to do, as presumably it's the most efficient, and is essential for doign things like showing spinner overlays/status overlay images on cells, etc.

Edit - I added a call to Layout.ForceLayout().. but it still ignores the y size of my gridview.