RelativeLayout Alignment

I am trying to do a bottom right alignment with a label on a relative layout

        Label status = new Label{ Text = "status", TextColor = Color.White };

        rlFront.Children.Add (status, 
            Constraint.RelativeToParent ((parent) => {
                return parent.Width - (status.Width + 2);
            }),
            Constraint.RelativeToParent ((parent) => {
                return parent.Height - (status.Height + 2);
            }));

But the Height and Width are always -1 as are the requested size.
This seems as thought it should be a simple and basic layout as it was in pre forms days.
What am I missing.
This is an extract of the first Item I need to place
Using a grid is not really an option as the design is based on relative positioning and not nice neat columns and rows.