Twenty Thirteen header image alignment

Hi All
I have an header image I’d like to use in the twenty thirteen template but I’d like to have it left aligned and not centered.

I think I fond a solution:

I changed the file

\wp-content\themes\twentythirteen\inc\custom-header.php

in the function twentythirteen_admin_header_style()

change the block

<?php
if ( ! empty( $header_image ) ) {
echo 'background: url(' . esc_url( $header_image ) . ') no-repeat scroll top; background-size: 1600px auto;';
} ?>

into

<?php
if ( ! empty( $header_image ) ) {
echo 'background: url(' . esc_url( $header_image ) . ') no-repeat scroll left top; background-size: 1600px auto;';
} ?>

(added left between scroll and top)

Now the background image of the header is nicely left aligned!
I cannot link the site because I am still working on my local machine, I have not yet this site on a host.
I am not a big expert, so if anyone can see a problem or a risk with this solution please advise!

Ciao
Marcello