Sources about the Roxolani/ leather armour

[Dan Howard]

I have 2 types one a leather lamellar which has 4mm thick scales and is tanned not rawhide and is less weight than my segmenta. Where as my horn scale lorica weighs as much as my short hamata but is very rigged.

It weighs less because it provides a lot less protection. Any hide armour that protects as well as a segmentata weighs a lot more than a segmentata. 4mm isn't thick enough for proper armour unless you use a construction with a dense overlap so that any attack is presented with three layers of scales, or you lace the scales to a leather backing, which provides an additional layer of protection.