Simon that was not our group, that was a different bunch of Aussies!
I have no idea how the Pittman Building was so named. My theory is that it was named in memory of a C.I.A. officer killed in the line of duty (Xin Loi). Many firebases were named after deceased individuals, but that is only a guess. Also for Americans Pittman would be easier to comprehend than a Vietnamese name or address, no matter how clever C.I.A. operatives were.
Next time you are in Saigon you must go up there.