Armor and Encumbrance
If a character is wearing more than one piece of armor at a time, only the highest value (for either Bludgeoning, Piercing, or Slashing) applies. Note that some armor items, like helmets and shields, provide a modifier to the worn armor rating and so do not count as stacked armor.
Too much armor, however, can slow a character down. If a character’s total armor base rating exceeds his Body, apply a –1 modifier to Agility and Reaction for every 2 points (or fraction thereof ) that his Body is exceeded. Note that this may affect Initiative as well.
If a character is wearing multiple armor items, add their ratings together before comparing to Body.