Hi,
The counterpart we need to contribute is a letter by our lawyer and favorably a letter from EFF or some other bigger organization guaranteeing Tor is what it is and we as client do not try to fool them.
as the US government sponsored (parts of) the Tor development - what about giving them US military research papers about the Tor network?
http://www.dtic.mil/dtic/tr/fulltext/u2/a465464.pdf is one of them, co-authored by a Navy researcher and performed by the Naval Research Laboratory.
Not itself sufficient, but done by a bigger organisation w/o triggering anarchist/commie/hacker/terroristsupporting/publicenemy bias reactions.
Renke