Snippet to add Fixed amount of weight to the WooCommerce order. PluginHive plugins - https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/, https://www.pluginhive.com/product/woocommerce-fedex-shipping-plugin-with-print-label/

functions.php

/**
 * Title : Snippet to add Fixed amount of weight to the order.
 * Created at : 25 June 2018
 * Updated at : 25 June 2018
 * PlugiHive Plugins : https://www.pluginhive.com/product-category/woocommerce-plugin/
 * Gist Link : https://gist.github.com/xadapter/f330a6f529dfa9199a30ec2fa9fca3ef
 */

add_filter( 'wf_customize_package_on_cart_and_checkout', function( $package ) {

	$weight_to_be_added_to_order = 0;		// Weight which needs to be added to the order.

	$weight_to_be_added_to_each_product = $weight_to_be_added_to_order / count($package['contents']);

	foreach( $package['contents'] as &$line_item ) {
		$line_item['data']->set_weight( (float) $line_item['data']->get_weight() + $weight_to_be_added_to_each_product );
	}
	return $package;
});

Is there any way to make this workable for multi-carrier shipping plugin? I would like to add 2 lbs to any order within a specific class.