Cybereyes capacity cost & cyberlimbs

Question

In SR4 it is possible to buy cyberlimbs, and customize them with upgrades that cost a certain amount of capacity (noted [X] in relevant tables) rather than essence. This is different from a capacity available for installing mods (noted X, without square brackets.)

A cyberskull seems appropriate to house a pair of cybereyes, but I can't find any capacity costs for them. Cyberskull capacity and cybereye capacity seem unrelated since the skull has a capacity of 4, and a rating 4 cybereye has a capacity of 16, so I don't think it may be used as a capacity cost.

Augmentation p.38 talks about single cybereyes, telling:

Single cybereyes may also be installed in other parts of the body, independent of the character’s usual (cyber)eyes. These additional cybereyes can be implanted almost anywhere on a character’s body.

1. Do cybereyes always cost essence, no matter where they are installed?
2. If not, what is the capacity cost for cybereye(s)?

Answer 1

Well, a cyberskull is not an actual replacement of the entire head:

Cyberskulls and –torsos are included in this category, though they are in fact shells rather than full replacements.

This means that organs - including eyes and brain - are not replaced when taking a cyberskull, and the loss of Essence of having your eyes replaced is not included in the cyberskull's Essence cost. Therefore, having your eyes replaced by cybereyes would incur the normal Essence cost.

Two houseruling sidenotes:

• Considering the original Essence cost comes from having your eyes removed, it could be houseruled that adding cybereyes to your cyberskull in addition to your own eyes would take Capacity instead of Essence (nice way to watch your back). As it would be a houserule, there is no official ruling for this, but I think cybereyes taking an amount of Capacity equal to their Rating could be fair.
• Cybereyes are not necessary for visual enhancements (although it then costs Essence). You could theoretically houserule than visual enhancements can be added directly to the cyberkull, taking an amount of Capacity equal to their original Capacity cost.