How do I load multiple esm's? in FO3, it was finding bAllowMultipleMasters in the ini, but, I can't seem to find this in any of the ini files. Or, am I just missing something?

Considering I can load FalloutNV.Esm and CaravanPack.Esm I think they fixed it so you just can. Have you actually tried? I think it will let you.

Sorry for the long reply, but, yes, I tried and you can't.

Is there a fix for this? or, what ini file do I need to modify?

GECKCustom.ini > bAllowMultipleMasterLoads=1

Thanks, that worked!