Support Forum

You could set the smaller image size for the columns, then use a function to set a larger image size for the featured post:

add_filter( 'wpsp_image_attributes', 'tu_featured_column_image' );
function tu_featured_column_image( $atts ) {
    // Set up our conditional
    if ( ! is_singular() && in_array( 'featured-column', get_post_class() ) ) {
        $atts[ 'width' ] = 1200;
        $atts[ 'height' ] = 400;
        $atts[ 'crop' ] = true;
    }

    // Return our options
    return $atts;
}