I have read a little on shimming the Koiguchi. My katana (a customized Bugei Bamboo) has no friction whatsoever between the habaki and koiguchi. I have read the different areas that some people suggest shimming (I have heard pros and cons for shimming on the sides versus the ha and mune sides).

My questions are:

What type of wood do use for this? And what is recommended adhesive/glue?

Many thanks for any input you can provide.