I have modified metallurgy 4's carmot to have lightweight and well-established successfully

carmot:head:established
carmot:handle:lightweight
carmot:extra:established

However, doing the same to prometheum does not work

prometheum:head:crude
prometheum:extra:crude
prometheum:handle:crude

I have verified not only that the material is referred to as 'prometheum' internally, but also that the trait is referred to as 'crude' internally.
Modlist

You'll have to use crude1 (or crude2) because crude is a trait with levels. I'm pretty sure all traits with levels require numbers.