I don't know what you mean by "boot/heel" morph. That picture looks like they turned the limits off for the feet and just bent the foot down and the toes up.  Have you tried that?

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi