So, I'm putting together a Mycenaean kit, and I'm quite taken with the skirts worn by the warriors on one of the frescoes at the palace at Pylos. This is the reconstruction:
Now, at first, I reckoned that these man-skirts were just black and white, something I could replicate easily. Looking at the original fragments, however, it really seems that the black portion of the skirt is a different layer than the white underlayer:
When you look at other contemporary pieces, you even see that such black garments were worn independently, which further supports the theory that they are two separate pieces. For what it's worth, this suspicion is confirmed by the guy who did the Osprey book on the Mycenaeans. In his recreation of the scene, he envisioned the black as a sort of leather skirting-- perhaps a rudimentary "perizoma," a fringed armor belt. I think it's also feasible to interpret it as fabric-- maybe another layer.
So, I have a few options. I could make an armor-grade version of this piece. Frankly, I don't want to do that, as it would be too thick and heavy to hang correctly. Also, by the book, such an armor piece (at least one with strips spaced like that) wouldn't really do much:
3.3.4. Weapons that strike both Armored and unarmored Target Areas are considered to have hit the unarmored Target Area.
Of course, any hit I'd take to the thigh would likely hit both the armor and my leg, and, frankly, I think that taking the hit as armor would be cheating.
I could make it out of fabric.
Or, I could use the non-armor-grade leather I have lying around.
TL;DR: Is it actually in the rules that wearing non-armor grade leather as garb is forbidden (I couldn't find anything), or is it a convention? It's something I've heard from time to time, and I've never had a reason to investigate it.