Interesting question Rick, since every now and then we see hilts that appear to have a bit of age yet are made out of highly questionable materials. Could these be old "Rudy Valee" ukirans.
As to wrappings, sometimes i think it depends on how much space there is to fill. Sometimes you get a rather large hole with a fairly thin pesi. I usually use a cotton fiber cloth and finish with some magician's silk i've had around for a while. The silk is vey squishy when wrapped and has a lot of give. Then, i've got on blade where the fit of pesi to hilt is so matched that i use no material at all.
Marto mentioned hair which i find very interesting. I've had one keris that came to me this way. I like the idea of it from a magickal perspective. It is my understanding that this is a fairly recent practice (last couple of hundred years, 1800 on or so). Do you know any more about this Marto?