Okay scenerio:
Imagine a Troll with Orthoshin 3, and Titanium Bone lacing, wearing an armored jacket has an armor rating of (13/11) [(1/1) from troll + (3/3) from Orthoshin + (1/1) From titanim bone lacing + (8/6) from armored jacket].

Said troll gains immunity to normal weapons (Spirit pact, or hybrid/good merge with an insect spirit) lets say at force 4 for example. That's effectvely (8/8) of hardened armor.

Question: how does it combine?

Case 1:
Is it effectively (21/19) all hardened. (The non-hardened armor slows down the bullets/blows then the hardened armor shrugs them off).

Case 2:
Armor rating is effectively (21/19) but only 8/8 of hardened so any damage over 8 still must be resisted, but unless it exceeds 21/19 it's stun.

If case 2 is correct does AP Apply to the hardened part so if you have a modified damage of 8p and AP-1 then you get to do stun? Or does the AP get used up passing through the armored jacket, so that an 8p attack with ap -1 bounces off the hardened part...

i would say case 2, personally.

and in all probability, the AP would go towards the outermost layer first, provided it's a set number... in the case of the troll, that would be the armor jacket,

if it's a reduction based on armor (for example, 1/2 impact armor comes up a lot), then i would say it gets divided up between the various armors (so if someone shot the troll with stick-n-shock, i would treat the troll as having 4 points of hardened armor).

of course, this leads to the question.... what comes before what in terms of layers? obviously worn armor is outside of most things (force fields, possibly including magic armor spells and adept powers would be outside of that even, probably), and then i would say armor built into skin. in this case, i would place the hardened armor as the bottom layer, on account of it's immunity to normal weapons, not really armor at all per se.