Cyber body Mathematics, Working on my Cybersheet Options

[Nightwalker450]

I'm beginning the cyber body build sheet for my character creator now (available through signature link). Only a mathematical sheet is available currently, but I wanted to get some feedback early 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...