FWIW I do use Calibre, with my NC in airplane mode. But I use kiwidude's Modify Epub plugin to ensure that my cover has "taken". I mostly design my own book covers to ensure they're no degraded as so many that you get with your books are - and it's fun. I was constantly frustrated by the altered covers not showing up on both my NC and my Kobo Touch. The solution is easy.
In Calibre, edit metadata to choose any cover image you want, the go to the plugin and run it with "Insert or replace cover" checked. Also, I remove the SVG cover when converting to epub in Calibre. It's also a great way to change the metadata and place it at the front of the book as a jacket with the add/replace metadata option at the same time - and any other odds and ends you want.
Last edited by Hoods7070; 06-13-2012 at 07:43 PM.