WooCommerce - Change number of upsells displayed and # of products per row

functions.php

remove_action( 'woocommerce_after_single_product_summary', 'woocommerce_upsell_display');
add_action( 'woocommerce_after_single_product_summary', 'woocommerce_output_upsells', 20);

if (!function_exists('woocommerce_output_upsells')) {
	function woocommerce_output_upsells() {
	    woocommerce_upsell_display(3,3); // Display 3 products in rows of 3
	}
}