Changing setting of a Color Matte

I have some color mattes with rotoscopes embedded in them.

I now need to deliver to specs of a different comp siz and ratio.

If I could just extend the top and bottom of the Color Matte to match the new frame, it would make this very simple.

But I cannot find a way to modify the Color Matte size settings, only look at the properties and chagne the color itself, not the size.

Is there a way to modify the size parameters of a Color Matte after it's been created?