Shim with metal vs. wood?

I recently bought a loaded jazz body for a project. It is great in every sense except one: the neck pocket was routed 3/16" deeper than a standard Fender pocket. I tried it with my neck without any shim, but it's way too low in the pocket. I figured I could just cut a piece of wood to fit in the bottom of the pocket and re-bolt the neck like that, but then I had a thought. Has anyone used brass or aluminum for this purpose, and would it give you any additional advantage regarding sustain? I can rout a wood peice to fit, and I have access to someone who could cut a metal insert as well, so ease or availability is not really an issue, although it would be much faster for me to form the wooden insert. I just wondered if anyone else had tried this, and if it would would affect the tone or sustain positively or negatively. Thanks in advance!