To enable the new functionality of Import/Export in Hyper-V R2 (download), we now have new ‘Ex’ versions of the Import/Export APIs along with settings data objects that allow the user to tweak the necessary parameters upon export or import. Export: Before you run an export, you can get the export parameters associated with a VM in the form of a settings data object. They are populated with default values. You can modify the parameters you need and then call ExportVirtualSystemEx with the modified object passed in.
Full Article: WVT Blog