Centered look for Main Content in tokyo Layout

How can I make the Main Content area centered in the tokyo layout?

I tried creating a custom CSS file, adding .fullPageLayout{width:100%;} to it, but this class gets overridden by tokyo.css which has the following:

.fullPageLayout,.ms-blog-MainArea
{
    width:100%;
    max-width:74em;
}

If I try to comment the 74em part I get a warning that this will break the link with Site definition.