Hi, I'm creating a fixed-layout picture book for KF. I have it completely built (html for each spread; images in their folder; embedded fonts, content.opf, css style sheet, etc)

I discovered that I can create a mobi by opening a complete content.opf (manifest lists all elements; spine gives play order; correct metadata for fixed-layout, etc.) through Kindle Previewer. It looks good on the Fire; my question is: is this a 'real' mobi? Or is this too easy, and I need to do something more robust? Thanks very much.