...
There are settings to set FIR mode, but I don't have this documentation here to tell me how to make sure that it is used.
P.S. I remembered about an hour later that I put all the settings in the software wiki:
http://wiki.eol.ucar.edu/sew/ISFS/SensorInformation/NanoParo
These settings have now (2108) been applied, and the barometer is reporting at ~14sps.