UV's on GUI Image

We are looking to put a cropped (video) texture on the GUI layer. Essentially just cropping to a center square of the texture. This is easy when we are in 3d space by setting the UV’s on our mesh. Is there anything similar we can do on the GUI layer? Or would we need to use a second camera with a traditional / mesh and render that camera last on top of the scene. Perhaps there is something that can be done with advanced dynamic textures or render textures that we are overlooking?

Many thanks!

Actually we figured out we can achieve this simply using the source and scale properties available on image.