I'm a contractor working in Germany and just sent in my wife's N-400 under 319b (expedited naturalization) last month. The check actually just cleared yesterday. The Army passport office and MP station on base actually did a lot of the work for us by certifying many documents and completing the fingerprint cards. I also sent in a letter from my company and a copy of my LOI.
What company do you work for? I requested an interview at the Fairfax, VA office so we'll see how it goes.