Hi Finema - one possible route to get an IGES result would be to model it in polygons and then use the T-splines plug-in for Rhino to convert from a sub-d surface into NURBS surfaces which can then be exported to IGES.

It's difficult to create organic shaped bumps and lumpy forms in CAD programs, CAD programs are just more focused on precision profile curve driven shapes and such lumpy areas do not fit with the CAD toolset very well.

- Michael