I convert many books (epub to KindlePreviewer) to mobi format... but I'm having just one pesky problem... Chapter Headings... everything else is wonderful. When I tweak the epub (in Sigil) to show my Chapter Headings in the correct size (just a skosh bigger than the 100% body text), they look fabulous on the Previewer for all Kindle devices (of course not the iPad and iPhone)... however when I get them to my KindleFire to preview on an actual device, the 'skosh' bigger than 100% bodytext (or Normal) has suddenly gotten to be about 115% and bold. Why would this be? Is Kindle Previewer being accurate in its preview? It's a small thing, but I'm a perfectionist and my clients expect that from me!