All know that there is a possibility to launch Inventor Professional with series license - with key /aislicense in execute string in Inventor shotrcut.
In my opinion i found a method for launch Series Inventor with professional license: in registry HKEY_CURRENT_USER\Software\Autodesk\Inventor\RegistryVersion11.0\System\Preferences\License
cnahge value from 1 to 2 for key "MRU License Edition ". Tested with 11th version. Hope this info will be helpful.