The problem: After creating the blog, I realized that the content of the page only goes about two-thirds of the way across, with no way to update that while editing the page.
The solution: After a little poking around, I found the three styles that had to be updated to extend the blog posts to expand the full width of the page.
I added the following styles to my COREV15.css:
.ms-blog-MainArea {max-width:none;}
.ms-blog-postList {max-width:none;}
.ms-blog-MainArea>tbody>tr>td{width:100%;}
The two max-width styles were already listed, with a setting of 860px and 670px, respectively. I found those and replaced them with none instead of adding a second style.
I'm sure there are different and possibly better ways to do this, but it took care of what I needed. The end result:
