Moving armor around? I'm not sure I can see any way of doing that in a single hull. [...]
If the 4% layer is uniform all over the hull how do you move some of the AV from the back to the front?
In brief: note it on the ShipSheet. Page 352:
T5 p.352 said:Armor. Enter the AV Armor Value for each layer (Layer1 is leftmost on the table). The column labelled C should contain any Coating.
Armor can be repositioned, subject to the Gradual Restriction: Armor Layers at a Hit Location cannot exceed Armor Layers at adjacent Hit Locations by more than 1. For example, instead of all Hit Locations being assigned the same armor, one layer at Hit Location-4 can be re-allocated to Hit Location-3.
I think there may be an errata item in that text, but the intent is clear.