I've been experimenting on making a "lizardman"-type head as an accessory. After a whole lot of frustration, I finally got it to appear in-game. However, there's one last problem: his creepy, see-through eyes!
I've looked through some tutorials and made sure the relevant materials were set to SimStandardMaterial as well as setting stdMatAlphaBlendMode to none for all of them, but the eyes still display through the head and slightly transparent. It was made from a set of glasses and the eyes were made from the lens - could this have anything to do with it? I think it may also be still using the old texture from the set of glasses on the eyes as the lens was that yellow/orange color.