Again, nice formatting.
I did note, though, that one/line line paragraphs have no indenting, but three of more line paragraphs do have indenting. Is this an "option"/feature of GutenMark?
Also, if you're creating the .imp from .html using eBook Publisher, you can easily add margins or justify the text by changing the <body> tag, (see here eBook Publisher
for more customizations available when using eBook Publisher).
You will note that the header <hr> does not honour the rest of the ebook's margins. I found that if you define the <header> segment AFTER the <body> tag, it will.
Anyways, food for thought.
You're doing great work!