On Thursday, November 16, 2017 at 6:39:00 PM UTC-8, Bob La Londe wrote:
"whit3rd" wrote in message
...

I'd go with glass

Part of the concept is to be able to make the parts uniform thickness. Even
the insulating sleeve. I'm going to give phenolic a try.

One more option:
Ceramic standoffs (like https://www.mcmaster.com/#94335a151 ) come with
threaded holes, if you want something quick.