I think this requires a house rule.
I'm all for boosting the cyber based characters but adding the armor rating of each limb is ridiculous.
Here is what I propose:
Lower Arm, Lower Leg, Hand, Feet and Skull armor is only for when those specific body parts are targeted.
Base Armor rating benefit for character = (L Leg Armor + R Leg Armor + Torso Armor + L Arm Armor + R Arm Armor)/5 Round up.
Final Armor rating benefit = Base Armor Rating Benefit + (1 for 2 armored limbs, + 2 for 3 armored limbs, +3 for 4 armored limbs, +4 for 5 armored limbs) where armored limbs are arms, legs and/or body with at least 1 point of armor.
Armor availability is reduced to Rating * 3
Armor capacity is reduced to 0 for Obvious Limbs (it's on the outside)
I think this is generous to people with cyberlimbs but it doesn't make dermal plating, ortho skin, etc pointless.