Renaming docs converted to kepub

Hi,

Let me preface this by saying that the inbuilt ability of Calibre to convert to kepub on the fly is of no use to me. I use a wireless connection to transfer my books and something no-one ever mentions is that this conversion does not work over wifi.

I am considering changing the default book format in my Calibre library from epub to kepub. I notice though that when Calibre converts to kepub, the resulting file is a <title>.kepub, whereas the files on my Kobo tend to be <title>.kepub.epub.

Is there a way to instruct Calibre to change the default extension used when converting to kepub?