Your problem is the translation. None of the translation software specs cover all of the things you want to put into your model, so they don't get translated.
Get a copy of the STEP or IGES stanadrds and you will see waht they specify for translation entity types. Then compare what the spec says with what the exporting system says they translate. This is the maximum that will be imported, since the import system may not read all of the exported data.
UG even fails in certain areas. With IGES, UG has NEVER claimed to import the same data they export, round-trip the data. I have been on UG since V3 and they have been saying that round-tripping the data is not a good test for translator spec testing as long as I have been using it.
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