MSQ,
One supplier of Nomex (Aramid honeycomb) is R&G i Germany.
They have a lot of information on their internet site, including how to lay up Nomex honeycomb, what thickness materials to use for various applications etc.
Go to:
http://www.r-g.de/
look for Services, Downloads, R&G Handbuch-Edition8
Chapter 9 is the one you are after.
All in German and English.
Magne