Still need to apply the sealer on this guy, but I couldn't wait to get the mixed media on.
I bought some flat leather cord off Etsy that was just thin enough to thread through the holes on the codpiece. Was a royal pain in the neck since the codpiece is fixed where it is, but with a sewing needle and string, I was able to get a decent result. I only threaded the front and only through the outermost holes, each side wrapping around the back and terminating in a knot between the legs. Unfortunately Prime 1 attached the bone pouch to the belt, so I had to wrap over it.
The sash was interesting. We all know the bone pouch actually hangs from knotted leather cord hanging from beneath the chest armor. According to photo reference, the leather cord is knotted around a light-colored string. I tucked one end under the chest armor in the only spot where thread could fit (the armor sits extremely close to the skin for the most part) and tucked the other end in a small space between the bone of the pouch and his waist. Not sure how long it will hold at the chest without glue, but I could thread the leather about 1 cm behind the pouch's bone and the string about an inch!
As for the back, the armor sits too close to the skin for me to "continue" the sash there. Most of it would be covered by armor anyway, unless it sits above the armor in the back and then tucks under at his neck? Eh, it's a weird design.
Not touching the cord around his belt again, but I might experiment with the chest sash some more. Maybe see if I can cut the leather cord lengthwise so it's half the width, that ought to make the knots look more to scale.