[Feature request] Foreground X shift and zoom

[mykeehu]

I like your extension, but I'm missing one option: the X shift of the foreground, which would allow me to place it in a perfect position on the image without enlarging the background image.
(Unfortunately the Y shift doesn't work for me with one subject on the cropped image either, please check that too!)
It would also be nice if I could zoom in-out the foreground image instead of zooming in the background image (because I can only zoom in the background image up to a certain size because of the video card). Like a Z vector/parameter. A random zoom would also enhance the collage.

Thanks in advance if you can make it work!