Image Lost, EPUB to MOBI Conversion

[Knuckles McGinty]

I use SIGIL to build my books table of contents, add meta data, and add a marketing cover image on top of my internal content cover image. The finished EPUB looks beautiful in Calibre. The marketing cover image rests on top of the internal content cover image in accordance with my wishes.

Unfortunately, when I call upon Calibre to convert the book from EPUB to MOBI, the internal content cover image disappears. Why is this? Perhaps I should mention I use MOBI Pocket Creator to install a 'start' HTML hook to my internal content cover image. (The image right under the marketing image).