IPhone : Defining aspect of a custom container view inside a ViewController

I got a ViewController with a container. Whilst I am able to add autosize constraints for the ViewController I seem to be unable to set them correctly for the container ViewController.

Here is what I get in storyboard:

I would like to display the two labels lx and rx in the child ViewController but I can display only the bottom label.

It seem that the child view does not have the right aspect ratio.