If you are writing code against the API you really don't need my help!
1) I recall that loadMXF overwrote everything. I think I tried but couldn't use it to insert XML elements or subtrees. It might be able to, but I never discovered the command line switches or XML code needed to make it work.
2)Minimum entries. My hack relied on minimal changes to a fully functional XML import. When I tried trimming it down, it usually crashed.
3) I had a strong feeling that there was some code behind the import that linked tables and data in the EPG database that could not be controlled in the XML and loadMXF.
Final note, when troubleshooting other people's XML files, some of them were very different from mine. Whole sub-trees were in completely different places.
Sorry I can't be more helpful.
Samsung LN40A550, Asus A8N SLI, Athlon 64 X2 3800, XFX HD One 5450, 2 Hauppauge HVR-2250, LG BH10LS30 Blu-ray, Windows 7