Doug,
Typically the wind on the underside of an eaves overhang equals that on the adjacent wall surface. For example from ASCE7-05 Fig6-6 Cp=+0.8 for the windward wall, so soffit would experience Cp=+0.8 (upwards), whilst sidewalls experience Cp=-0.7 (downwards), and leeward Cp=-0.5(max. mag.) (downwards). Adopt similar approach for C&C pressures.
Not sure where rule is in ASCE7 but it is the approach used to AS1170.2, and I recollect something in commentary to ASCE7-05.
Regards
B.Tech (mfg & mech), MIIE, gradTIEAust
mailto:sch.tectonic@bigpond.com