so I'm getting a victory line bomber jacket, 3/3 with chemical protection 1 and insulation 1.
If I buy more chemical protection, do I have to start at 1 or can I add onto whats there?
also, if I have another piece of armor with chemical protection, do they stack?

AFAIK you would have to start over. There is this thing with ciber- and bio-wares that you have to buy the full package instead of buy level by level, so I would rule the same for armors.

Just my 2 ...

@ Stacking of armor mods: I'm pretty sure that only highest rating should count. It's the same with ballistic and impact armor ratings, if you leave aside things like FFBA.

On the other topic I'm with Brazilian_Shinobi, though this is a little more debatable. If you say a higher rating of chem. prot. comes from additional layers of chem.-proof fabrics than a case could be made to allow the upgrading of an existing chem. prot. If, on the other hand, you say improvement of chem. prot. ratings comes from the use of more advanced fabrics, you would have to start over and pay the full price for the new chem. prot. rating.

-CJ

I wouldn't allow stacking anything except FFBA, and that goes for mods.

IMO you should be able to stack them, but that mostly becouse i divade the mod limit of the armored clothing lines in arsenal between the invidual parts so i can know what my character loses if she takes the coat of the set of. So mostly i think they should stack, becouse that makes everythink much easier to me and really whats the difference between someone having armor with noncondactivity 6 and an FFBA with insulation 6 and the other guy who has noncondactivity3 and insulation 3 in both armors for the same combined effect, most of the time their conna be wearing the both armors anyway.

edit, cos Yerameyahu posted while i was typing:
Do you mean you allow mod in FFBA to stack with the mods in a normal armor, if so what else would you think people would mod to try and stack them other then their normal armor and the FFBA.
Unless you allow an universal stacking of armor(a house rule i personallly advocate for) i dont think the's anytink else to try and stack mods from.

No, I meant that only FFBA stacks (let's just pretend that PPP doesn't exist) for armor, and that no armor mods stack with themselves (Chem with more Chem, etc.).

I think the question was:

If I buy Chem 1 and want to upgrade to Chem 2, do I have to pay full price for Chem 2, or can I just pay the difference between Chem 1 (which I have) and Chem 2 (which I want)?

Oh, *upgrading*. Sorry. You always have to pay the full higher cost.

I have seen numerous people say that but I have rarely seen it backed up in the rules. Not that it matters to me all that much. I simply allow players to pay the difference unless it is a situation where a replacement, such as replacing a video card in a modern day computer, makes more sense than a true upgrade, such as adding more chemical protection to a jacket.

Because there's no rule saying you *don't* have to do a full replacement. (AFAIK; maybe there is.) Examples of other 'upgrades' in the book repeatedly support a full-replace concept, that's all. The 'logic' can easily go either way, because fluff is only justifying.