Hi I`m new to this forum and thread. Great find!
I've been working on IEMs for a little while now and I`m trying to acquire drivers which is difficult. So far the only easily accessible source I found is through digkey for Knowles drivers. Sonion is apparently only direct contact.
I made great progress of making good fitting acrylic shells, which is why I`m trying to move on with the project. I didn't have time to read through the whole thread, but I think I read that some people use epoxy as IEM housing material, which may not be biocompatible. You might get rashes or worse reactions. I will post some pics of my shells if there is any interest.
I think I also saw someone mentioning Hackerspace. I`m in SF so maybe there can be some local collaboration!