Put Books onto the device in 2 different formats

Hi,

I'm using a Kindle for reading books, but I want to read books in the native app as well as in koreader. This means I have to copy both .azw3 and .epub format of my books onto the reader (and no, I don't want to use the .mobi format).

How can I configure calibre to automatically copy both formats to the reader whenever I send a book to the reader?

Cheers, Joe