I'm beginning the cyber body build sheet for my character creator now (available through signature link). The sheet is not available yet, but I wanted to start posting my computations so I can get feedback earlier on.

And I'm trying to figure the mathematics for this sheet. So here's some theories, as I create this I'm going to be building it by my houserules to start with, and eventually add the options to put it so it is strictly raw.

So first the house rules, which are just being developed after participating in the normal forums:
Head / Cyberskull has no attributes: They should almost never be averaged in to anything, and its the internal workings that provide the body IMO. You still get the bonus damage box from the skull though.
Torso has no BOD Attribute: Again the internal workings are the Body, and a Cybertorso is a shell. Bonus Damage Box still provided from the replacement though.
Replacing a forearm or lower leg, will provide half a box (rounded up) to damage tracks. Wrists and Feet provide no boxes.

Ok, so all overall averages come from Torso + 4 Full Limbs. The BOD attribute from Torso is always the natural one.

The Full Limb has attributes of either the cyber replacement, or the average of Natural and Lower Limb.
The Lower Limb has attributes of either the cyber replacement, or the average of Natural and Hand/Foot.
So mathematically replacing just your hand will make the Full Limbs Attributes: 3/4 Natural + 1/4 Hand

Since this is all being done programatically, I'm letting its full complexity show. The numbers provided for averages will be rounded to 2 digits, and its up to the GM as to how they round...

I disagree with the "no Bod" thing. Body is what resists damage; in a normal head, this is the skull, and in a normal torso this is the ribcage, pelvis, spine and sternum (and the abdominal muscles). When you replace the skull with a cyberskull, you're explicitly replacing the part that resists damage. Likewise with the torso. I agree that the Skull should never contribute Agility or Strength.

but that Body is only used for damage resistance tests. Poison and disease resistance use your natural rating, as does damage overflow.

My contention is broken bones don't kill people, damage to internal organs, arteries, nervous system, etc is what kills people. Getting dents in your cyberskull will only affect you in so long as it damages the brain inside it. These are all reflected by adding armor to these shells to protect the actual Body portion. And as has been stated, adding armor to a limb adds directly to all tests, vs adding body just ups your average 1/5. Limbs have body in so much as the internal mechanics get damaged and the functionality of the arms are reduced, so it reflects the severing of vital systems.

Well, it's not the bone breaking that kills you; it's the attack penetrating past the bone. The Body test, especially for the head and torso, is basically to see whether the skeleton acts as a barrier.

Face it - anything that actually gets into the squishy bits is going to cause Damage boxes. The damage resistance test is to see whether those squishy bits get touched, and therefore it's pretty clear that the part that's actually doing the resisting is whatever's between the squishy bits and the pokey bits.

Look at it this way - if I took a professional boxer, and took his brain out of his skull, and took Professor Hawkings's brain out of his skull, and set them side by side in some nutrient-filled zip-lock bag, I don't think there would be any substantial difference in their ability to resist damage. Likewise if you take all their innards out of their chest/abdominal cavity. So clearly, it's the container that's protecting them. Does that make sense?