Liquify Image Tutorial Modification

The liquify image tutorial mentions, on page 2:

What if: instead of empty space behind the masked image, there were another image behind it? That other image behind it would show through. And with some sneaky layering:

I’m wondering if it’s possible to combine this with the liquify image effect so that, as you liquify the image, you discover new parts of the image ie: the image in the center circle is slightly different (say with a white area on it somewhere) than the main image.

I tried it, masked another image using that “sneaky layering” method, then tested the liquify script, and I got a circle that lagged behind all the others, sometimes catching up to the mouse, that displayed the image I wanted to show, while the rest of the effect worked as before.

So instead of that circle in the back, how can I make it show through the circle in the front? Is it even possible? Any suggestions are appreciated.