The previous posts are missing a step, i couldn’t get it to work at first and then some digging revealed that you need to modify one more file.
In the frontend/wpsl-ajax-function.php file you need to change line 67 from:
$thumb_src = wp_get_attachment_image_src( $result[$k]->thumb_id );
to
$thumb_src = wp_get_attachment_image_src( $result[$k]->thumb_id, $size->full );
Once i did this in combination with the above suggestions my full size images are now loading correctly.
