: Whenever someone says that Bungie-era MJOLNIR restricts movement too much, I
: wonder about the undersuit and how the armor plates are mounted to it.
: Does the outside surface of the undersuit move 1:1 with the body inside?
: Are the plates hinged and bolted onto sliders so as to give the user
: uninhibited range of motion?

Are you asking what Bungie did or what 343 does or how it works in universe?

I don't know the answer to any of those questions but I could guess...

The Halo 3 armor is just a paint job, the armor plating has no depth (at least it doesn't on the legs). This makes the Chief look like he is built like a brick shithouse and is wearing spandex armor.

The Reach armor looks more 3d. I can't remember if there are any clipping issues.

The 343 Spartans are pretty thin and get their body-builder bulk from the armor. I like this approach. Obviously they do look like red cobs when the armor is removed but, for me, this isn't a problem. I have never seen a red cob in-game. A 343 post or vi-doc said that they went this route to avoid clipping problems.

The 343 Chief looks really athletic under his armor. He is lithe rather than bulky. I prefer that look to the brick shithouse Chief (f I was the Chief, that's how I'd want to look).

Now, as for in-game speculation...

I think that some of the pieces would be articulated (on sliders or movable arms). It makes sense.

If memory serves... Our knee caps have a small muscle above them that position the knee cap as we move. Our quad muscles also attach to it but I think there is a little make-sure-its-in-the-right-position muscle as well. Spartan shoulder pieces could have something similar, something fail safe that ensures that things just work when the Spartans moves their arms.