Thanks odamizu and KevinH!
I am now looking for a volunteer to help debug the KFX conversion output plugin.
I need a Mac user who has the Kindle Previewer 3.0 beta installed and is familiar with using calibre to convert books from one format to another. This will require manually installing a beta test version of the plugin that I will send via PM on Mobileread, trying it to convert
a specific book to KFX using it, and reporting back to me on the results or errors produced via PM. It will probably take several iterations to get it working.
I'd like to work on this with a just one person to avoid a lot of back and forth on the forums. Once it is working I will make the plugin available in the calibre plugins forum.
I'll send the beta test plugin to the first person who indicates their interest in helping.