You see a lot of kozane from the Meiji period just strung together. Most kozane from heian onwards were made with supporting bars etc. what you need to consider Cameron is that kozane offered very little ballistic protection to the wearer. After 1545 armours had to change, mostly replacing kozane for mono-ita. Yet oddly iyozane was still widely used. Also most gessan are made from rawhide. During sengoku testu was scarce, so you see plenty of recycling. I've seen examples of ashigaru armours fitted with would have been the most expensive hon kozane gessan due to this reason.
Rule 1 of katchu is that there are no rules as such. You will always find an example that destabilise the norm. Also edo was a period of bespoke, recycling and adapting.