How to use feeds tamper to set default value from importer node?

I've got a number of feeds that I want to be able to import regularly. I setup feeds and attached them to a content type, ex. "My Feeds" which imports into another content type, "Article".

I also need to make sure that when these feeds come in, that I can set the default values in the target node. The use case is that I will be importing from feeds in multiple languages and want them associated with an author so I have created a couple of new fields in my importer content type:

field_languagefield_author

I want to be able to set the language and author value for each feed when I create the importer and have those associated every time I update but its not clear if any of the existing plugins do this.

I've also started writing my own custom plugin to pull in these values from the parent importer but I can't figure out how to access or load the importer object through a feeds tamper plugin.

Any pointers or is there a better way to acccomplish this task?