hi fcoulter, welcome to the forum. if you only want to make mobipocket files, why not just use the mobipocket creator application ? it's available as a free download on the mobipocket site : http://www.mobipocket.com/en/downloa...ilsCreator.asp
kindle can read drm-free mobipocket files.
of course, if you want to make both epub *and* mobipocket, you might be better making epub first, then converting it to mobipocket. be aware that mobipocket can't handle some advanced formatting you can do in epub.