In the IBC 2003, I don't believe OMF will apply to your situation. The 15 psf floor issue is for footnote i which is for SDC D, E and F. (difers from IBC 2000)
I have a very similar situation.(IBC 2003, SDC=D) I can use IMF or SMF that are pre-qualified in FEMA 350. BUT IMF connections are not...