hello
If you're in Windchill 10, thinks you can do like that:
-update the ResourceBundle QuantityUnit to add your Imperial unit in the list of Units available in WTpart BOM link
-Do not create Bulk Items as CADDocument with owner link
-create directly your bulk item as a WTpart in the BOM with the desired quantity and Unit and mark it "not for built" in the Product Structure Explorer (the owner association and the Build from CAD will not remove this bulk part)
Do not remember the Build process in 8.0 ...
Don't think you can do the same ....cause the "not for built" feature does not exists, so the Build process systematically remove the bulk WTPart (thats why the TPI ....)
regards