I do have a question, though ... and not trying to be insulting. What is the benefit of learning how "not to be moved?"
This seems tacky/insulting to say, but "Best way block punch, you no be there." Right? It's always seemed best to me. I know there are certain jutsu branches out there that seem to specialize in "hit me and you can't hurt me" but that smacks of the arms race between armor-piercing vs. armor with armor-piercing always coming out on top.
I've always quite liked Peter Ralston's approach to this in Cheng Hsin - yielding works with every attack - the "won't be moved" approach tends to find eventually the one person who can move you! That said, when he was training for full contact competition (1978 when he won), he learnt qigongs and iron shirt methods to lessen injury.