[Theming Snippets] Change number of upsells output
add_filter( 'woocommerce_output_related_products_args', 'wc_change_number_related_products' );
function wc_change_number_related_products( $args ) {
$args['posts_per_page'] = 1;
$args['columns'] = 4; //change number of upsells here
return $args;
}