I've not had chance to check this out yet, but it may be helpful to fellow Eigen-harpers:
CreateDigitalMusic - SFZ Player and public format
The bit that struck me from an Eigenharp perspective is one of the bullets that mentions drag-and-drop conversion to SF2. I'm going to have a look during the holidays, but has anyone else already tried this?
EDIT: just re-read with my brain engaged and it's actually conversion from SF2 rather than to, which is less useful, but it may still be a useful tool.