Recent post blocks within section block – alignment issues

Hi all. I’m currently working on a simple theme for a personal photography/travel writing site. I’m using the Chaplin theme by Anders Norsen as a starting point.

I’ve got some issues arising when I place a (wide width) latest posts block within a (full width) section block. As you can see, the posts block is the correct width but aligns to the left rather than in the centre of the section block. The same things is happening with the header I’ve placed there.

Any idea on a fix here? I believe this has something to do with the setting of margins – I’ve tried a few changes in the custom CSS class but to no avail.

The page I need help with: [log in to see the link]